To write a Japanese address on an envelope, follow this format, writing from largest geographical area to smallest, and from top to bottom:

1. Recipient's Name (宛名 - ate-na): Write the recipient's full name in Japanese characters (Kanji, Hiragana, or Katakana) clearly and legibly. If you only have the name in Roman letters (Romaji), transliterate it carefully, ensuring accuracy. Place this at the top center or slightly to the right.

2. Postal Code (郵便番号 - yūbin bangō): Write the seven-digit postal code in Arabic numerals. Enclose it in a rectangle or underline it for clarity. This should be placed below the recipient's name, usually aligned to the left.

3. Prefecture (都道府県 - todo-fu-ken): Write the name of the prefecture (e.g., 東京都 - Tōkyō-to, 大阪府 - Ōsaka-fu, 北海道 - Hokkaidō). Use the standard Japanese name, not a shortened version.

4. City, Ward, or Town (市区町村 - shi-ku-chō-son): Write the name of the city, ward (ku), town (chō), or village (son). This follows the prefecture.

5. Street Address (丁目番地 - chōme banchi): This includes the street name, building number, apartment number, etc. Be precise and include all relevant details. The order is typically "street name," "chōme" (block number), "banchi" (lot number), and then apartment or building number. For example: 〇〇町1-2-3-401 (〇〇chō 1-2-3-401).

6. Building Name (建物名 - tatemono-mei): If applicable, write the name of the building (e.g., 〇〇ビル - 〇〇 Building).

7. Company Name (会社名 - kaisha-mei): If sending to a company, write the company name above the address components.

Important Considerations:

• Writing Style: Use block letters (楷書 - kaisho) for the best readability. Avoid cursive writing.
• Language: While Romaji can be used, it's generally preferred to use Japanese characters (Kanji, Hiragana, Katakana) for the address. If using Romaji, ensure accurate transliteration.
• Clarity: Write neatly and legibly. Ambiguity can lead to delivery delays or failure.
• Order: Maintain the strict top-to-bottom, largest-to-smallest geographical order. Any deviation can cause problems.
• Sender's Address: Write your return address on the back flap of the envelope in the same format, but in your native language.
• Special Characters: Pay close attention to the correct use of characters, especially for similar-sounding place names.
• Verification: Before mailing, double-check the address for accuracy. A small mistake can significantly impact delivery.

Example:

(Recipient's Name) 〒100-0001 (Postal Code) 東京都千代田区〇〇町1-1-1 (Prefecture, City, Street Address) 〇〇ビル 5階 (Building Name, Floor)

Remember to replace the example place names and details with the actual recipient's address information. Using online translation tools can help with transliteration, but always double-check the accuracy.