Thank you very much davidfor.
It is totally doesn't work even in Japanese books. I have checked other Japanese books and confirmed it. All of my kepub.epub books, which work properly in terms of bookmarks and last pages, are converted by certain converters like
Kobo Touch Extended Driver and
KePub Outtput Plugin. They wrap a span around each sentence.
The reasons why I mistook it were as follows
1) I have both automatically converted and manually converted kepubs together in my kobo.
2) I don't check the difference between sleep, power off and home position. It totally doesn't work after power off.
3) Chapters are so short.
4) Many Japanese sites recommend to change extensions from epub to kepub.epub manually for Japanese books without any attention about bookmarks.
I will never change the extension from epub to kepub.epub manually. Thank you very much.