The above comments illustrate my sentiments exactly. These antagonists belong in an NTR scenario, nothing to do with a sharing route, as their motives are to keep MC away from Evelyn, by subterfuge, denying him the opportunity to partake in actual sharing. Rather just have him presented as a willing cuck.
Diana and Evelyn had already decided to fuck the boss, by themselves, before consulting MC, even though in my playthrough, I had Evelyn and MC avoiding any interaction with the boss. And then Brandon comes along as yet another one, not there to share, just to take. Diana set all this up at the beach. She is the one putting MC as a cuck, and giving Evelyn all the motive and opportunity to make him one.
MC should have punched the boss on the nose, as soon as he said it was "his meal", taken Evelyn away immediately, and told Diana to get fucked too. Evelyn wasn't "caring", she was pushing, in my view. MC in these scenarios, can only be seen as a cuck, not a lover.
The commenters who say that cucking is part of sharing, obviously have cheating and NTR scenarios as their preference, not sharing, no matter what they say, sharing is not cucking. Cucking is a thing all of its own, and should always be a separate choice.
There are many here who play sharing games, and with one or two exceptions, under certain circumstances, are not the kind who actively seek to be cucked.