To be fair, what would be illegal (actually, in many countries I'd say not illegal, but against school regulations) would be them actually dating. Being a love interest is NOT illegal.
Sensei can't teach me love ( https://mangadex.org/title/32726/sensei-wa-koi-o-oshierarenai ) has a similar premise. The teacher and student are "dating" but not really, it's platonic until he graduates.
@ShiroVn idk i kind of feel like it's not fair to call any of them true love interests, seeing as it would be illegal. that's why i can't get 100% behind this series, the only way to get a proper happy ending is to skip ahead a few years.