[ja] Apply 6f68925573e02c9e7398300f08272a4482851d52
[ja] Apply 483a4e4fc219c058fad7275f3b31db86f71e9283
[ja] Apply d3673c08144c67ef818e785214f90ed1832c6b24
[ja] Apply 0c34253095f327209aceab8b3170f93b0c0c4ed9
[ja] Apply 51ba3fa4cc2fb203f8c377d5a937bf5f3425526d and fix typo
[ja] Apply b294744d98a6f6cdbc3508b0058f8616147c1596
[ja] Apply 8ec0ce6bfcd7944193a95a4794bf2cc88e874362
Merge pull request #414 from harupong/ja-chapter9

[ja] Update chapter9
Merge pull request #415 from harupong/ja-chapter7

[ja] Update chapter7