DualBook 8 languages

Free online tool — no sign-up

Translate a Japanese book into English

Upload a Japanese EPUB and get the first fifteen pages back in English. Japanese leaves out what English insists on — subjects, plurals, who is speaking — and only the surrounding book can supply it.

The first 15 pages of text are sent to our server to be translated. The file itself stays on your device.

Japanese omits the subject whenever context makes it obvious. English cannot. So every dropped subject is a small decision the translator has to make, and a model working one paragraph at a time makes it blind: it guesses who is acting, and a wrong guess reads as a completely different scene.

Reading the whole book first is what supplies that context. So is the speech level: keigo, plain form and rough speech carry the entire relationship between two characters, and English has to smuggle that into word choice instead. Deciding it once, for the whole book, keeps a formal character from suddenly sounding casual.

Honorifics are their own choice — keep -san and -senpai, or render them. There is no right answer, only a consistent one, and consistency is what a guide built from the whole book gives you.

How it works

  1. Choose your Japanese EPUB

    A DRM-free EPUB. The file stays on your device; only the text is sent.

  2. The model reads the whole book

    Who each character is, how they speak and how they address each other — the context Japanese leaves implicit and English demands.

  3. The first 15 pages come back in English

    About 4,500 words, translated as continuous narrative so dropped subjects are filled from the scene, not guessed per sentence.

  4. Download, or read it here

    A complete EPUB with the original's styling intact.

What this free tool does not do

Vertical text and ruby are preserved, not translated. The file keeps its own stylesheets, so a vertically-set book stays vertical — but furigana above a kanji belongs to the Japanese and does not carry into English.

Fifteen pages, not the book.

Dropped subjects are inference, not certainty. The guide narrows the guesses; it does not eliminate them.

The text is sent to a server and discarded when the job ends.

Questions

Does it keep -san and -senpai?

It decides once for the whole book and stays with that decision. Which way it goes depends on the book's register, but it will not keep them in one chapter and drop them in the next.

What happens to furigana?

Ruby text belongs to the Japanese original and has no English equivalent, so it does not carry across. The untranslated remainder of the file keeps its ruby untouched.

Does a vertically-written book survive?

Yes. We change only the text; the book's own CSS, including vertical writing mode, is left exactly as it was.

Is it usable for light novels?

Yes, and they benefit more than most: light novels lean hard on speech level to characterise, which is precisely what reading the whole book first preserves.

Translate the whole book

The app translates the entire book with the same engine and keeps the Japanese beside the English for checking.

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