You know the story is at least somewhat interesting when the comments section is already getting heated within the first few chapters.👺
It's likely too early to tell for sure, but Seiko is giving off some yandere vibes. Concering Fukiishi's interest in Seiichi, he's probably been giving her the childhood crush stares from quite awhile now, and she's obviously noticed it here and there. Him interrupting that other dude at the pool was the trigger she was looking for to express her own interest, in him. After all, Seiichi seems like a nice normal-looking kid, is able to make friends, is pretty smart, and not a jerkass; it's completely natural for her to want to see what he's about.