this is perfectly fine? kinda feel like the "trap rei" stratagem has a certain lifespan, but this isn't toxic at all? like, kaya more or less confirmed she didn't like her boyfriend at all, and the boyfriend cheating there is well in the "maybe you should admit the relationship is fucked, but you fucked instead" area. that's understandable at least. that kind of avoidance is a very human flaw and just pretty shitty instead of incredibly shitty.
more or less, rei acted completely ethically. homewreckers can't expect to be liked by people, but are hardly the party at fault. rei's claim that she can only trust people who stay with her after she's hurt them is kinda toxic, kinda suggestive of backstory, and kind of wrong in this case? kaya isn't really hurt, and rei should know this. stealing someone's boyfriend from the trash can isn't stealing, and everyone knew that boyfriend was heading for the trash can. which means rei is a thieving cat only because its cute for her to be one.
is the kaya/rei relationship likely to work out? honestly, no. will it be worth it to both participants? probably. is it going to be as toxic as other commenters think? no, rather its likely to die from either devolving into friendship, or into just another of rei's relationships. probably the only romantic one, but maybe the only non-sexual one. kaya's open jealousy makes it hard to tell if she's ace enough and poly enough to be rei's only romantic relationship sans sex. doesn't really seems like it if she's plotting to avoid sex to trap rei instead of that being a preference. feel like the trap can't last and the question is, what then?