Japan Phone Number Format: Complete +81 Validation & Area Code Guide

Japan phone numbers use the +81 country code and follow a structured 10-digit format for landlines and mobile numbers. This comprehensive guide covers Japanese phone number validation, area code hierarchy, carrier integration, and MIC regulations for developers building telecommunications services in Japan.

Understanding Japanese Telecommunications Infrastructure

Japan boasts a highly sophisticated telecommunications infrastructure, overseen by the Ministry of Internal Affairs and Communications (MIC). This robust system adheres to ITU-T E.164 standards with country code +81 and supports a massive mobile market, with 188.9 million mobile connections as of January 2024. This makes Japan one of the most connected nations globally, presenting both opportunities and challenges for developers.

Japanese Mobile Carriers and Market Share

The Japanese telecommunications market is highly competitive, dominated by three major carriers: NTT Docomo, KDDI (au), and SoftBank. These carriers invest heavily in infrastructure development, driving innovation in areas like 5G and IoT. Additionally, Mobile Virtual Network Operators (MVNOs) play a significant role, offering competitive pricing and specialized data plans.

Major MVNO Providers:

• IIJmio: One of Japan's most established MVNOs, offering plans on both Docomo and KDDI networks
• Rakuten Mobile: Originally launched as an MVNO in 2014, became a full MNO in 2020; surpassed 8 million subscribers by October 2024
• Mineo: Popular MVNO offering triple-carrier support (Docomo, KDDI, SoftBank)
• Y!mobile: SoftBank subsidiary offering competitive mid-range plans
• UQ Mobile: KDDI subsidiary with reliable service
• OCN Mobile: NTT Communications MVNO service

MVNOs accounted for approximately 7.3% of the market in March 2024, with online/digital-only MVNOs holding 53.69% of MVNO market share.

Sources: Mordor Intelligence Japan MVNO Market Report, Rakuten Mobile Press Release Oct 2024

pie title Market Share Distribution (March 2024)
    "NTT Docomo" : 40.6
    "KDDI (au)" : 30.6
    "SoftBank" : 21.5
    "MVNOs & Others" : 7.3

Source: Ministry of Internal Affairs and Communications (Japan), published June 28, 2024

Key Technical Specifications:

• Country Code: +81
• International Access Prefix: 010 (for calling from Japan to other countries)
• Domestic Long-Distance Prefix: 0 (trunk prefix)
• Total Number Length: 10 digits (including area code, excluding country code)

Japanese Phone Number Formats Explained

Japanese phone numbers follow a structured format based on geographic regions and service types. Understanding these formats is the first step towards accurate validation and processing.

How Japan Area Codes Work

Japan uses a hierarchical area code system, reflecting the geographic distribution of its population. Area codes generally increase from north to south across the country:

• Single-digit: Major metropolitan areas (e.g., 3 for Tokyo, 6 for Osaka – displayed as 03 and 06 with trunk prefix)
• Two-digit: Large cities and regions
• Three-digit: Medium-sized cities
• Four-digit: Rural areas and smaller municipalities
• Five-digit: Smallest municipalities and remote areas

This hierarchical structure allows for efficient routing and identification of calls originating from different parts of the country. Shorter area codes are assigned to densely populated regions, while longer codes serve less populated areas.

Major City Area Codes:

Source: Wikipedia - Telephone numbers in Japan

Common Japanese Number Formats by Type

The following table illustrates common number formats and their typical usage:

Additional Special Service Prefixes:

• 0570 (Navi Dial): Shared-cost service for call centers and customer support; charges approximately ¥10 per minute from mobile phones; domestic-only (not accessible internationally)
• 0180 (Teledome/Telegong): Automated information services and TV/radio show feedback dial-in; toll charges apply
• 0990 (DialQ2): Premium rate services; typically charge ¥90-200+ per minute depending on service provider; used for entertainment, information services, and adult content
• 0120/0800: Toll-free services (free for caller, costs borne by recipient)

Source: Wikipedia - Telephone numbers in Japan

Important: Mobile prefixes (070, 080, 090) were expanded from the original 090-only range to accommodate growing mobile subscriber demand. All three prefixes are equally valid for mobile numbers.

How to Validate and Integrate Japanese Phone Numbers

Integrating Japanese phone numbers into your application requires careful consideration of carrier requirements, validation patterns, and emergency service integration.

Number Portability (MNP) in Japan

Implementing telecommunications services in Japan requires addressing number portability, a system that allows users to retain their phone numbers when switching carriers. This system, regulated by the MIC, is crucial for ensuring service continuity and consumer protection. You must design your database to accommodate number portability data.

MNP Lookup API Providers:

Since number prefixes no longer reliably indicate the current carrier due to portability, you must use MNP lookup services. Several international providers offer MNP lookup APIs for Japan:

• HLR Lookups: Provides real-time MNP lookup with original and current network information including MCC/MNC codes
• Seven.io: International MNP lookup service for routing optimization
• Horisen: Worldwide MNP lookup with fast response times
• BSG World: MNP Lookup API identifying current serving operator and portability status
• Carrier-specific APIs: NTT, KDDI, and SoftBank may provide direct lookup services for enterprise customers

// Required Database Structure for Number Portability
{
  phoneNumber: string, // E.164 format recommended
  originalCarrier: string,
  currentCarrier: string,
  portingHistory: Array, // Array of porting events
  lastPortingDate: timestamp,
  lastMNPCheck: timestamp // Cache MNP lookups to reduce API calls
}

// Example MNP Lookup Integration (Pseudocode)
async function checkMNPStatus(phoneNumber) {
  try {
    const e164Number = toE164Format(phoneNumber);

    // Check cache first (MNP data valid for 24-48 hours typically)
    const cached = await db.getMNPCache(e164Number);
    if (cached && isCacheValid(cached.lastCheck)) {
      return cached.carrierInfo;
    }

    // Query MNP API
    const mnpResult = await mnpAPI.lookup(e164Number);

    // Update database
    await db.updateCarrierInfo({
      phoneNumber: e164Number,
      currentCarrier: mnpResult.currentNetwork,
      originalCarrier: mnpResult.originalNetwork,
      lastMNPCheck: Date.now()
    });

    return mnpResult;
  } catch (error) {
    console.error('MNP lookup failed:', error);
    // Fallback to prefix-based detection (less accurate)
    return getPrefixBasedCarrier(phoneNumber);
  }
}

This structure allows you to track the porting history of a number and identify the current carrier, which is essential for accurate routing and billing. Remember, always store phone numbers in E.164 format internally for consistency and interoperability.

Sources: HLR Lookups MNP Documentation, BSG MNP API Docs

Japanese SMS Encoding and Character Limits

Integrating SMS/MMS functionality requires understanding encoding limitations and carrier specifics. Japanese SMS uses UCS-2 (UTF-16) encoding for character representation, as the standard GSM 7-bit encoding only supports English and Western European languages.

Character Limits:

• UCS-2 (UTF-16) encoding: 70 characters maximum per message segment (required for Japanese characters)
• GSM 7-bit encoding: 160 characters (ASCII-only, not suitable for Japanese)
• Concatenated messages: Multiple segments automatically linked for longer messages

SMS Concatenation Details:

When messages exceed the single-segment limit, carriers automatically split them into multiple parts. However, concatenation uses header information that reduces the available character space:

• Single UCS-2 segment: 70 characters
• Concatenated UCS-2 segments: 67 characters per segment (3 characters used for concatenation header)
• Single GSM-7 segment: 160 characters
• Concatenated GSM-7 segments: 153 characters per segment (7 characters used for header)

Source: Vonage Japan SMS Features

MMS Size Limits:

• Maximum message size: Typically 300KB to 5MB depending on carrier
• Recommended size: Under 300KB for best compatibility across all carriers
• Supported media types: JPEG, PNG, GIF images; AMR, MP3 audio; 3GPP, MP4 video
• Text limit in MMS: Up to 1,600 characters (much higher than SMS)

Source: Industry standards for MMS messaging

Important considerations:

• Shift-JIS is used for email on some legacy systems but not for SMS
• UTF-8 is not widely supported in SMS; most carriers use UCS-2/UTF-16
• Each Japanese character (hiragana, katakana, kanji) counts as one character in UCS-2
• Emoji and special characters also count as one character each

// Calculate SMS segment count
function calculateSMSSegments(message) {
  const hasUnicode = /[^\x00-\x7F]/.test(message);

  if (hasUnicode) {
    // UCS-2 encoding
    const singleSegmentLimit = 70;
    const multiSegmentLimit = 67;

    if (message.length <= singleSegmentLimit) {
      return { segments: 1, charsPerSegment: singleSegmentLimit };
    } else {
      const segments = Math.ceil(message.length / multiSegmentLimit);
      return { segments, charsPerSegment: multiSegmentLimit };
    }
  } else {
    // GSM-7 encoding
    const singleSegmentLimit = 160;
    const multiSegmentLimit = 153;

    if (message.length <= singleSegmentLimit) {
      return { segments: 1, charsPerSegment: singleSegmentLimit };
    } else {
      const segments = Math.ceil(message.length / multiSegmentLimit);
      return { segments, charsPerSegment: multiSegmentLimit };
    }
  }
}

You should implement delivery receipt handling and cross-carrier message routing support. Test thoroughly with Japanese characters to ensure proper encoding.

Phone Number Validation for Japan (+81)

Accurate validation is crucial for preventing errors and ensuring data integrity. While simple regular expressions can handle basic validation, a more robust approach is recommended for comprehensive validation. Consider using a dedicated library like libphonenumber-js (supports multiple languages including JavaScript/TypeScript) or building a comprehensive validation class in your chosen language.

// Comprehensive Japanese phone number validation (Example)
class JapanesePhoneValidator {
  constructor() {
    // Mobile prefixes: 070, 080, 090
    this.mobilePattern = /^(070|080|090)-?\d{4}-?\d{4}$/;
    // IP telephony: 050
    this.ipTelephonyPattern = /^050-?\d{4}-?\d{4}$/;
    // Geographic (simplified – actual area codes vary)
    this.geographicPattern = /^0\d{1,4}-?\d{1,4}-?\d{4}$/;
    // Toll-free: 0120, 0800
    this.tollFreePattern = /^(0120|0800)-?\d{3}-?\d{3,4}$/;
  }

  validateNumber(number) {
    // Handle null/undefined input
    if (!number || typeof number !== 'string') {
      return { isValid: false, reason: 'Invalid input: number must be a string' };
    }

    // Remove spaces and hyphens for validation
    const cleaned = number.replace(/[\s-]/g, '');

    // Check total length (should be 10-11 digits with trunk prefix)
    if (!/^0\d{9,10}$/.test(cleaned)) {
      return { isValid: false, reason: 'Invalid length' };
    }

    // Determine number type
    if (this.mobilePattern.test(number)) {
      return { isValid: true, type: 'mobile' };
    } else if (this.ipTelephonyPattern.test(number)) {
      return { isValid: true, type: 'ip_telephony' };
    } else if (this.tollFreePattern.test(number)) {
      return { isValid: true, type: 'toll_free' };
    } else if (this.geographicPattern.test(number)) {
      return { isValid: true, type: 'geographic' };
    }

    return { isValid: false, reason: 'Unrecognized format' };
  }

  toE164(number) {
    // Convert to E.164 format: +81XXXXXXXXX (remove leading 0, add +81)
    if (!number || typeof number !== 'string') {
      return null;
    }

    const cleaned = number.replace(/[\s-]/g, '');
    if (cleaned.startsWith('0')) {
      return '+81' + cleaned.substring(1);
    }
    return null; // Invalid format
  }
}

// Example usage
const validator = new JapanesePhoneValidator();
const result = validator.validateNumber("090-1234-5678");
if (result.isValid) {
  console.log(`Valid ${result.type} number`);
  console.log('E.164 format:', validator.toE164("090-1234-5678"));
  // Output: +819012345678
} else {
  console.log('Invalid:', result.reason);
}

This approach allows for more flexible and accurate validation, handling various number formats and edge cases. Test your validation logic thoroughly with various valid and invalid number formats, including numbers with hyphens, spaces, different prefixes, and edge cases like numbers with too few or too many digits.

Japan Emergency Numbers and Caller ID

Integrating emergency services requires priority routing and adherence to specific regulations. All emergency numbers must be accessible even when the device is locked or has no active SIM card – this is a legal requirement in Japan.

Emergency Numbers (Must be supported):

• 110: Police (112 and 911 redirect to 110 on mobile phones)
• 118: Maritime emergencies (Japan Coast Guard)
• 119: Fire and Ambulance services
• 171: Disaster Emergency Message Dial (earthquake/disaster communication)

Technical Requirements Based on MIC Standards:

According to the IETF Draft on Emergency Call Requirements for IP Telephony in Japan:

1. Priority Routing (MUST1): Emergency calls MUST be routed to the correct Emergency Call Reception Office (ECRO) covering the caller's location
2. Failover Support (MUST2): Calls MUST redirect to alternative facilities if the primary ECRO is unavailable
3. Keeping Connection (MUST4): Emergency calls MUST NOT terminate unless ECRO terminates them, even if the caller hangs up
4. Reversing Call (MUST5): ECRO must be able to ring the caller's terminal during "keeping connection" state
5. Location Information (MUST8): Geographical location information MUST be presented to ECRO, including:
   • Fixed IP-phone: subscriber name, address, address code (JIS standard), telephone number
   • Portable/Mobile IP-phone: subscriber name, location dispatch info, telephone number, coordinates (latitude/longitude/altitude)
6. Call Priority (MUST10): Emergency calls MUST have priority over all other calls
7. Provider Identification (MUST3): IP telecommunication provider info MUST be presented to ECRO

Implementation Example:

// Emergency call handling
function handleEmergencyCall(phoneNumber, callerLocation) {
  const emergencyNumbers = ['110', '118', '119', '171'];

  if (emergencyNumbers.includes(phoneNumber)) {
    // Set highest priority
    call.priority = 'EMERGENCY';

    // Route to correct ECRO based on location
    const ecro = getECROByLocation(callerLocation);

    // Include location data in call setup
    call.locationInfo = {
      latitude: callerLocation.lat,
      longitude: callerLocation.lng,
      altitude: callerLocation.alt,
      accuracy: callerLocation.accuracy,
      address: reverseGeocode(callerLocation),
      addressCode: getJISAddressCode(callerLocation)
    };

    // Enable keep-alive even if caller disconnects
    call.keepAlive = true;
    call.allowReverse = true;

    // Override caller ID restriction
    call.forceCallerID = true;

    // Log for compliance
    logEmergencyCall({
      timestamp: Date.now(),
      callerID: getCallerID(),
      location: call.locationInfo,
      routedTo: ecro
    });

    return establishEmergencyCall(call);
  }
}

Testing Emergency Number Handling:

Never test emergency numbers by actually dialing them. Instead:

• Use network simulators or test environments provided by carriers
• Implement unit tests that mock emergency call scenarios
• Use designated test numbers provided by MIC-certified testing facilities
• Validate call routing logic through code reviews and static analysis

Source: IETF Draft - Emergency Call Requirements for IP Telephony Services in Japan

Caller ID Control: Japan supports caller ID control through special prefixes:

• 184: Withhold caller ID (prefix before dialing)
• 186: Provide caller ID explicitly (prefix before dialing)

Example: Dial 184-03-1234-5678 to call with caller ID hidden.

Ensure your application complies with all relevant MIC regulations regarding emergency service access. Non-compliance can result in significant penalties and service suspension.

Best Practices for Japanese Phone Number Integration

Beyond the technical requirements, following best practices ensures a smooth and user-friendly experience.

Converting Between E.164 and Local Format

Always store numbers in E.164 format internally (e.g., +819012345678). However, display numbers in local format for Japanese users with hyphens for improved readability (e.g., 090-1234-5678).

Format Conversion Rules:

• E.164 to Local: Remove +81, add leading 0, insert hyphens based on number type
• Local to E.164: Remove hyphens and spaces, remove leading 0, add +81

Hyphen Placement by Number Type:

• Mobile (070/080/090): 0X0-XXXX-XXXX (e.g., 090-1234-5678)
• Tokyo (03): 03-XXXX-XXXX (e.g., 03-1234-5678)
• Osaka (06): 06-XXXX-XXXX (e.g., 06-1234-5678)
• 2-digit area code: 0XX-XXX-XXXX (e.g., 011-123-4567 for Sapporo)
• 3-digit area code: 0XXX-XX-XXXX (e.g., 052-123-4567 for Nagoya)
• 4-digit area code: 0XXXX-X-XXXX (e.g., 04992-1-2345)
• IP Telephony (050): 050-XXXX-XXXX (e.g., 050-1234-5678)
• Toll-free (0120): 0120-XXX-XXX (e.g., 0120-123-456)

// Format conversion functions
function toLocalFormat(e164Number) {
  if (!e164Number.startsWith('+81')) {
    return null; // Not a Japanese number
  }

  // Remove +81 and add leading 0
  const national = '0' + e164Number.substring(3);

  // Apply hyphenation based on prefix
  if (/^0(70|80|90)/.test(national)) {
    // Mobile: 0X0-XXXX-XXXX
    return national.replace(/^(0\d0)(\d{4})(\d{4})$/, '$1-$2-$3');
  } else if (/^03/.test(national)) {
    // Tokyo: 03-XXXX-XXXX
    return national.replace(/^(03)(\d{4})(\d{4})$/, '$1-$2-$3');
  } else if (/^06/.test(national)) {
    // Osaka: 06-XXXX-XXXX
    return national.replace(/^(06)(\d{4})(\d{4})$/, '$1-$2-$3');
  } else if (/^0\d{2}/.test(national)) {
    // 2-digit area code: 0XX-XXX-XXXX
    return national.replace(/^(0\d{2})(\d{3})(\d{4})$/, '$1-$2-$3');
  } else if (/^050/.test(national)) {
    // IP telephony: 050-XXXX-XXXX
    return national.replace(/^(050)(\d{4})(\d{4})$/, '$1-$2-$3');
  }

  // Default fallback
  return national;
}

function toE164Format(localNumber) {
  // Remove all non-digits except leading +
  const cleaned = localNumber.replace(/[^\d+]/g, '');

  if (cleaned.startsWith('+81')) {
    return cleaned; // Already E.164
  } else if (cleaned.startsWith('0')) {
    return '+81' + cleaned.substring(1);
  }

  return null; // Invalid format
}

Implement automatic format conversion for international calls. When displaying international numbers to Japanese users, use the international format with country code (e.g., +1-555-123-4567 for US numbers).

Mobile Number Portability (MNP) Implementation

Implement prefix-based carrier detection, but maintain an updated carrier prefix database as prefixes can change over time. Crucially, handle number portability scenarios to ensure accurate routing.

Number Portability in Japan:

• Mobile: Launched October 24, 2006
• Fixed-line: Launched March 2001
• Users can retain their numbers when switching carriers
• Requires querying a Number Portability database to determine current carrier
• Important for accurate call routing and billing

Recent Regulatory Changes:

• April 1, 2021: MIC eliminated MNP fees as a general rule and mandated completion of online procedures within 24 hours
• Traditional "Two-Stop Method": Still available; requires obtaining an MNP reservation number (valid for 15 days)

MNP Process and Service Continuity:

During the porting process (typically completed within 24 hours for online procedures):

• SMS service: May be temporarily unavailable during the transfer window (usually 1-4 hours)
• Voice calls: Brief interruption (5-30 minutes) during the actual port activation
• Data services: Generally maintained throughout, though may experience brief reconnection
• MNP reservation number validity: 15 days; process must complete within this window

Users should be informed that brief service interruptions may occur during porting, and they should avoid initiating ports during critical communication periods.

Sources: Rakuten Mobile MNP Guide, MIC regulatory updates

Implementation Note: You cannot reliably determine the current carrier from the number prefix alone due to number portability. Use carrier lookup APIs or databases maintained by telecommunications associations.

Error Handling and User Feedback

Implement graceful fallback mechanisms for invalid numbers. Provide clear error messages in both Japanese and English. Log validation failures for monitoring and troubleshooting.

Common Error Scenarios and Responses:

// Comprehensive error handling
function validateAndFormatNumber(input, userLocale = 'ja') {
  const errors = {
    en: {
      empty: 'Phone number is required',
      invalid_format: 'Please enter a valid Japanese phone number (e.g., 090-1234-5678)',
      invalid_prefix: 'Invalid area code or prefix',
      too_short: 'Phone number is too short',
      too_long: 'Phone number is too long',
      international_not_supported: 'Only Japanese phone numbers (+81) are accepted'
    },
    ja: {
      empty: '電話番号を入力してください',
      invalid_format: '有効な日本の電話番号を入力してください（例：090-1234-5678）',
      invalid_prefix: '市外局番またはプレフィックスが無効です',
      too_short: '電話番号が短すぎます',
      too_long: '電話番号が長すぎます',
      international_not_supported: '日本の電話番号（+81）のみ受け付けています'
    }
  };

  try {
    if (!input || input.trim() === '') {
      return {
        isValid: false,
        error: errors[userLocale].empty
      };
    }

    const result = validator.validateNumber(input);

    if (!result.isValid) {
      const errorKey = result.reason === 'Invalid length'
        ? (input.length < 10 ? 'too_short' : 'too_long')
        : 'invalid_format';

      return {
        isValid: false,
        error: errors[userLocale][errorKey]
      };
    }

    return {
      isValid: true,
      formatted: toLocalFormat(validator.toE164(input)),
      e164: validator.toE164(input),
      type: result.type
    };

  } catch (error) {
    // Log error for monitoring
    logger.error('Phone validation error:', error);

    return {
      isValid: false,
      error: errors[userLocale].invalid_format
    };
  }
}

Retry Logic and Rate Limiting:

When integrating with external APIs (MNP lookups, carrier validation):

// Retry with exponential backoff
async function apiCallWithRetry(apiFunction, maxRetries = 3, baseDelay = 1000) {
  for (let attempt = 1; attempt <= maxRetries; attempt++) {
    try {
      return await apiFunction();
    } catch (error) {
      if (attempt === maxRetries) {
        throw error;
      }

      // Exponential backoff: 1s, 2s, 4s
      const delay = baseDelay * Math.pow(2, attempt - 1);
      await new Promise(resolve => setTimeout(resolve, delay));
    }
  }
}

// Rate limiting
const rateLimiter = {
  requests: [],
  maxRequests: 100, // per minute

  async checkLimit() {
    const now = Date.now();
    this.requests = this.requests.filter(time => now - time < 60000);

    if (this.requests.length >= this.maxRequests) {
      throw new Error('Rate limit exceeded. Please try again later.');
    }

    this.requests.push(now);
  }
};

Timeout Handling:

// Timeout wrapper for API calls
function withTimeout(promise, timeoutMs = 5000) {
  return Promise.race([
    promise,
    new Promise((_, reject) =>
      setTimeout(() => reject(new Error('Request timeout')), timeoutMs)
    )
  ]);
}

Frequently Asked Questions

What is Japan's country code for international calls? Japan's international country code is +81. To call Japan from abroad, dial +81 followed by the phone number without the leading 0.

How many digits are in a Japanese phone number? Japanese phone numbers contain 10 digits (including the area code) when written in domestic format with the leading 0. In international E.164 format, they appear as +81 followed by 10 digits.

What are the mobile phone prefixes in Japan? Japanese mobile numbers use three prefixes: 070, 080, and 090. All three are equally valid for mobile phones and were expanded from the original 090-only range to accommodate subscriber growth.

Can I keep my phone number when switching carriers in Japan? Yes. Japan's Mobile Number Portability (MNP) system allows you to retain your phone number when switching carriers. The system launched October 24, 2006 for mobile numbers and March 2001 for fixed-line numbers.

What encoding does Japanese SMS use? Japanese SMS uses UCS-2 (UTF-16) encoding, not Shift-JIS or UTF-8. This limits messages to 70 characters per segment, including Japanese characters, emoji, and special characters.

What is Tokyo's area code? Tokyo uses area code 03 (displayed with the trunk prefix 0). The single-digit area code 3 reflects Tokyo's status as a major metropolitan area in Japan's hierarchical numbering system.

Conclusion

This guide provides a comprehensive overview of Japanese phone numbers and their technical implementation. By following these guidelines and best practices, you can ensure seamless communication with Japanese users and build robust, reliable telecommunications services.

Next Steps for Developers:

1. Review MIC official documentation: Visit the Ministry of Internal Affairs and Communications website and their Technical Regulations Conformity Certification page
2. Obtain MIC certification: For telecommunications equipment, consult TELEC (Telecom Engineering Center) for conformity certification
3. Integrate MNP lookup services: Select an MNP API provider from the list in this guide
4. Test thoroughly: Use carrier-provided test environments and validate compliance with MIC requirements
5. Stay updated: Monitor MIC announcements for regulatory changes affecting telecommunications services

Official Resources:

• Ministry of Internal Affairs and Communications (MIC) - Primary regulatory authority
• TELEC - Radio Equipment Conformity Certification - Certification services
• ITU Japan Numbering Plan - Official numbering documentation
• IETF Emergency Call Requirements for Japan - Emergency services technical specifications

Consult these official resources for the latest technical specifications and regulatory updates before deploying telecommunications services in Japan.