Group sex and harem aren't the same thing. None of these girls are exclusive to the MC other than maybe Lancy but I wouldn't be at all surprised to find her working in the brothel at some point "for training purposes". Vivi has no business even being on the island. And all other girls only do stuff for coins.
By implication I mean the whole setup of this island is that boys and girls fuck for points and coins. All girls are supposed to have partners. And some of the girls are prostitutes who will fuck any dude for coins. The MC even thinks to himself the girls will fuck for money.
For the harem tag the game must give the MC a path where he can make girls exclusively his. Not just when they're with him, but at all times. The girls must be aware of each other and accepting of the situation. At least 3-4 girls are needed to qualify for the harem tag.
The MC thus far has shown himself to have the character of a horny 13 year old virgin. He's shown zero interest in making any girl his. He just wants to fuck as many as possible. That is not harem.
Katie is the only girl that fuck for coins.
(If you are implying that keisy and lancy would just fuck anyone for coins, nope.. it is shown in first episode when keisy doesn't want to do challenges with her perverted partner.)
The other prostitute girl Luna is an NPC.
Vivy do have but it not revealed yet.
I am making side stories for the 2nd version as I focused alot on the story on 1st version. I want players to be able to explore all challenges before I continue with the stories.
Yes, all girls have partner, but i just did not show it yet. I mean it just seems like there is endless things that I should show to you guys to make it logical..
But oh well, cant please everyone.. I'll just continue making !