No, seriously dude, it's called "fragile ego". Has it ever occurred to you that the captain doesn't care who they're sleeping with because he's not in a relationship with any of them and is just having fun? It's become so fashionable to write "cuck" now that people are literally going crazy in their obsession, as if everyone around them belongs to them. It makes me scared that such people will start going out onto the streets in real life and taking revenge on their "LI", who don't even know about these people, for "cheating".
Guys, get some help. Harem does not exist, all the girls in the world do not belong to you and if you want fidelity, then start a real relationship, get married, and do not accuse 2D characters of cheating and people who came for porn in cuckolding.