It's so realistic, it hurts. Tbh why I'd feel uneasy having a relationship with the seme is that he immediately tries to hook up with someone else to move on. I know decent people who would just give themselves time to even go on dates because they were indeed in love. So it's an understandable thing for the seme to do, but his actions might be interpreted as shallow feelings
I think it's because each individuals have their own way in handling their own feelings, considering the seme who seems to be so used in hooking up, I'm honestly not surprised. Some People forget by indulging themselves in pleasure. I don't think seme is very in love that time tbh, it's more of an object of interest at first and it isn't weird because you don't magically become deeply in love with someone without time invested on each other.
While most people are bothered about what thw seme did, i honestly think what he did was normal- He got rejected and tbh maybe he just tried to see if he can move on since there's no point in clinging at someone who turned you down cleanly and told ypou to find someone else, it clearly conveys that there's no chance of reciprocating his feelings. After fucking others, seme realized that it can't be just anyone else. Realizing it after trying is exactly the reason how he realized it. What's there to feel disappointed about when they weren't together to begin with? it isn't cheating and he did nothing wrong. It's just sex with no feelings involved.