Katakana to ASCII Romaji Shift-JIS Converter Online

What is Katakana to ASCII Romaji Shift-JIS Converter Online?

This agent converts katakana characters into plain ASCII romaji strings using a fixed, per-character substitution table. It is built for the specific situation where Japanese katakana text has to survive an 8-bit Shift-JIS environment that cannot carry the original characters, so each kana is replaced by a short ASCII stand-in. The result is not normal romanized Japanese spelling; it is a mechanical, reversible-in-principle encoding where voiced kana end in a backtick and semi-voiced kana end in an apostrophe.

Unlike a two-pane web translator that only shows a result, this agent explains every mapping it applied, keeps characters it cannot map instead of deleting them, and can walk the encoding back to katakana when you ask for the reverse direction.

Key Features

• Complete katakana table. Half-width and full-width katakana are both handled, including small kana, the prolonged sound mark, and half-width punctuation such as ｡ ｢ ｣ ､ ･.
• Documented diacritic convention. Voiced kana become uppercase romaji plus a backtick (ガ → KA`), and semi-voiced kana become uppercase romaji plus an apostrophe (パ → HA').
• No manual spacing workaround. You paste your text and get clean output directly, without inserting spaces and deleting them afterward.
• Preservation and reporting. Latin letters, digits, spaces, punctuation and any unmapped symbol pass through unchanged and are listed so nothing disappears silently.
• Character audit. A short table shows each input character, the output string, and which rule produced it.
• Labeled reverse reconstruction. Ask for the reverse direction and the agent rebuilds katakana from the mangled romaji, flagging anything ambiguous.

How to Use

1. Paste your katakana text into the message box. Half-width (ｶﾀｶﾅ) and full-width (カタカナ) forms can be mixed freely.
2. Read the converted ASCII string in the code block. Copy it directly into your Shift-JIS-bound field, file name, or configuration value.
3. Check the audit table if a character looks unexpected, then ask for a refinement such as keeping punctuation unmapped or switching to the reverse direction.

Example Use Cases

• Preparing katakana labels for a legacy Shift-JIS field. Convert a product name like ガッコウ into GAKKOU-style ASCII so it fits a field that rejects multibyte characters.
• Debugging a mangled romaji string. Paste an existing string such as KA`TTE and ask for the reverse reconstruction to see which katakana it came from.
• Checking half-width versus full-width consistency. Run both ｶﾞｯｺｳ and ガッコウ and confirm they produce the same ASCII output before committing a data migration.

Tips for Best Results

• Keep the original katakana in your message so the audit table can be checked against it.
• If your downstream system needs lowercase output, ask explicitly; the default table uses uppercase for base kana and lowercase for small kana.
• Remember that this is a mechanical encoding, not standard Hepburn romanization: シ becomes SI, ツ becomes TU, and ッ becomes tu.

FAQ

What input format does it accept?
Plain text containing katakana, either half-width or full-width, mixed with any other characters. There is no file upload; paste the text directly.

How accurate is the conversion?
It is exact for characters present in the fixed table, because the mapping is applied literally rather than guessed. Characters outside the table are preserved and reported rather than converted.

How is this different from some free text tools?
Some free text tools show only a two-pane result and leave the diacritic convention unexplained, and at least one asks you to insert spaces and remove them afterward. This agent returns clean output, documents the backtick and apostrophe rules, and reports unmapped characters.

Can it translate Japanese sentences into English?
No. It performs character substitution only; it does not translate meaning.

Can it produce font files or audio?
No. The output is plain text.