Shikibu
Shikibu opens a Japanese EPUB and puts the furigana where it belongs — above the kanji, in your edition, without changing a character of the text. Look up a word while you read, keep your own vocabulary, and let the dictionary explain why a reading wins. Everything runs on your machine; nothing is sent anywhere.
Complete tool, not a trial
Open an EPUB, add furigana with one click, keep per-book glossaries and your own vocabulary lists, and export a book that still passes epubcheck. The free edition carries a working offline dictionary for the words you meet most.
The full local database · a key that works offline
Pro unlocks the complete on-device Lingua Mundi lexicon — 291,960 Japanese entries with ranked readings and the evidence behind each one — so lookups are instant, unlimited and offline. Your licence key is verified on your machine: no account, no server, no phone-home.
Install the .deb or run the .exe. The app is offline after install: no account, no cloud, no telemetry. Your books, notes and glossaries stay in files you own.
Android: Shikibu 1.0.0 APK. Pro buyers receive the Pro build together with their licence key.
Requirements: Linux (amd64) or Windows 10/11 · Android 8+ · ~400 MB disk · 2 GB RAM · fully offline after install.
First run: install, open a Japanese EPUB, choose “Add furigana”. The editor writes ruby above the kanji and leaves the text untouched; export re-validates the book so it still passes epubcheck.
Bought a Pro key? Paste it in the app's licence dialog. Verification is offline — the key is not checked against a server, so it keeps working if this site ever goes away.
The dictionary behind Shikibu is Lingua Mundi, our lexical database: every reading it gives carries the evidence that produced it. The research paper describes the method.
Questions or feedback: rhls.softdev@gmail.com