[ja] Translate ebook/01.1.md into japanese.
[ja] Translate 01.{2,3,4} into Japanese.
[ja] Translate the 1st section into Japanese. (complete)
[ja] Translate 02.0.md into Japanese.
[ja] Translate 02.1 into Japanese.
[ja] Translate 02.2 into Japanese.
[ja] Translate 02.3 into Japanese.
[ja] Translate 02.4 into Japanese.
[ja] Translate 02.5.md into Japanese.
[ja] Normalize `next chapter`.