>>538100670
>Hiroy
It's plainly an "ehehe" or "hehehe" laugh

In Japanese it's written "ehehe" which fits her characterization a lot better than teehee
Ehehe is a slightly nervous laugh, a slightly neurotic character, or a mysterious character, it tends to give off a certain feeling
It fits hiyori who always feels like she doesn't deserve to be happy, so any happiness she feels just feels a bit odd to her like it can end at any time, and she's always worried about bad luck hitting her. She gives off a nervous yet earnest laugh.