You know, being a guy who has only ever hung out with boys, I am having a really hard time relating to this manga.
Do 5th graders really have such complex love concepts?! I have no idea how 5th grader girls IRL feel about romance. (Not that I have any idea how a grown up girl would feel now.)
5th graders are at an awkward stage in life where puberty is a thing for some but not all, and the concept of love exists only on a one dimensional plane. I hung out with p much anyone regardless of gender back then (and throughout my whole life really), and I remember being grilled about love in ways that feel absolutely asinine to me both now and then but to the average 5th grader were probably the best they could do
To people around that age, love can mean any number of one thing: you fall in love, get married, and have kids. Boys and girls can never be friends, or else they fall in love. Things are always in absolutes, there are no complexities. Love is simultaneously something that is supposed to happen and something that is embarrassing and worth teasing or bullying over.
Of course, as a queer person who knew I was such as far back as like 9 or 10 years old, all of this was ridiculous to me, but given how much I was teased and grilled about it, I have a pretty good understanding of how kids seem to think of love: like a weird game you play that has very little deep meaning beyond obligations and media depictions.