I wanted to ask to those who found out on their own (no guide) how to get the achievement: what exactly in the game suggested you how to do it?

I got it because I unwittingly read how to in an unrelated thread. I don't like getting achievements like this, it felt like cheating, but then I realized I would have never found out on my own.

I thought about getting all the fragments in the correct order the first time I played, even though in the end I didn't do it because I didn't care enough. But apparently you had to do it AFTER completing the game? Nope. IMO there was no clue in the game that suggested to do that.

I was trying to follow what appeared to be a clue in the brief part in the end where Hanyuu says she's still not satisfied and wants to be even more happy "in the near future", it made me think I had to wait some minutes after it, but it was completely off. So how did you do it?