“First book” in Japanese
Short answer
First book in Japanese is “上巻” (joukan). Full meaning: first volume (in a two or three-volume set), first book, volume one, book one.
Other ways to say “First book” in Japanese
正編
seihen main part (of a book), principal part; original text (as opposed to its sequels), first book (of a series)
正篇
seihen main part (of a book), principal part; original text (as opposed to its sequels), first book (of a series)
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