From what I understand, the island is magical; it will corrupt the couple depending on the choice, leading either to the wife or the husband cheating. It influences the minds of both, and it would be interesting to see the influence that leads her to cheat on her husband or him to cheat on his wife.
The island, being magical, could alter the husband's body, making him more corrupt and submissive, weaker with a smaller penis, while the MC becomes more corrupt and confident with a larger penis. The model that I liked the most and seems more natural is that of the guys from the club of the MC and Derek; it looks more like rubber.
To be honest, I don't like the humiliation of the MC, but that's a preference. However, I have to say that Derek's scenes have been intense since he doesn't pay attention to the text; the MC's scenes are still weaker, but in the 'harem' route, there is room for growth regarding the effects of the island.
Look, in the harem route, there is the possibility for the wife to be shared with other men if the MC is the guy with the magical and larger 'tool' like Derek, which is interesting.
We already have the MC displaying Beta behavior or being more normal in the other routes in the harem route.
In the nightclub during the conversion on the Harem route I would be willing to exchange couples since it is also picking up the wife of another guy, a threesome MMF that is not Derek's style with SPH humiliation of the small penis or MC sexually incapable, wife with other guys or as reinforcement of ego and confidence of the MC and the player the wife tries another guy and sees that the MC or in some benefit for the interesting MC.
The wife can have two routes: being a submissive cuckold, which is similar to the cuckold husband's route, or a Cuckquean, a wife who likes to know and see that other women are desiring and having sex with her man. She has confidence and knows that the MC loves her.
There are a lot of harems, especially where the MC has no interaction between NPCs and no reaction from the girls with the single-sex MC. I would prefer you to develop the relationship between the MC and the cuckold wife or Cuckquean. I mainly want her to be happy, where the MC takes her to a romantic dinner with her ass full of cum covered with a butt plug, where the MC caresses her pussy during the meal and speaks words of love, and then a trip to the nightclub where they pick up a dripping slut for a threesome, and she ends up forcing him to clean her cum-soaked pussy when she ends up receiving caresses from the MC until she falls asleep.