Clean up Japanese text inconsistencies in your spreadsheets — no formulas or scripts needed.

Features:
- Full-width alphanumerics/symbols → half-width (e.g. `０３（１２３４）` → `03(1234)`), and the reverse
- Half-width katakana → full-width (`ﾃﾞｰﾀ` → `データ`, with correct voiced-mark composition), and the reverse
- Whitespace cleanup (ideographic spaces → ASCII, collapse runs, trim)
- Hyphen unification for phone/postal numbers (protects katakana long vowel marks)
- Japanese era ⇔ Western year conversion (`令和6年7月25日` ⇔ `2024/7/25`, strict era-boundary handling, `R6.7.25`-style shorthand supported)

Privacy by design: all processing happens inside your sheet. No data is ever sent to external servers. Access is limited to the currently open spreadsheet only. Text cells only — numbers, dates and formulas are never modified.

Support: https://seitondo.com/support