I agree, jealousy is a natural emotion, and it's the actions that can be harmful. But listen to the mc's female friend, too: she was 100% when she said the ML's acting like his dad (extra points for noticing despite not even knowing their relationship). Acting like you're your lover's dad = acting controlling on your lover (which, if you blink twice can so effing easily and so effing quickly escalate into blaming your lover for "making you insecure with their behavior"). The point is... jealousy isn't always shown by starting fights with the 3rd parties (the perceived love "rivals"), rather than that, it's more often than not the jealous boyfriend confronts his lover, instead, turning all his frustration and anger directly on them, blaming them for "making them insecure". It starts harmless and even sounds "cute and caring" the first couple of times...till it becomes a tiresome, stress-inducing pattern and it just doesn't look "cute", anymore. Even in cases when it doesn't escalate to actual physical violence, it's already a toxic dynamic on the verbal side (when the couple start a cycle of always having toxic communication with each other).
damn guys, jealousy is a normal human emotion to feel but how someone chooses to act on it can make it harmful. so far seme hasn't started fights or FUCKING MURDERED SOMEONE (i thought he was just hella horny, didn't know other people interpreted that as murderous) over his jealousy. matter of fact, his reactions have been relatively harmless so far.
i'm kinda sad to some of the reactions in the comments. idk if it's just the loud minority complaining about the seme and dropping this but i do hope that's the case :( i rather like this couple