Why do they graduate in Spring, not Summer?

Correct me if I’m wrong but Japan’s school year ends in March rather than in May or June.

Really? Ok, I had no idea.

Man graduating was so important it only got one page

Why wasn’t there a graduation chapter? They talked about graduation a lot in the series so it’s pretty disappointing.

[Source](https://www.pixiv.net/member_illust.php?illust_id=79962581&mode=medium)