It's with the MC knowing and there. There won't be content with two girls alone in a room. There are people who can think that brushes the boundaries of NTR/Sharing. If there was a week-long discussion about two girls kissing I don't want to repeat it with two girls fucking.
It was planned from the start that there won't be any pure lesbian scenes (I love them, but when I began planning the game I wasn't sure I could pull it off with enough quality).
The lesbian content will be in threesomes/foursomes/Xsomes always with the MC there.
If the lesbian content is enabled, he can share but he will be there.
The 'lesbianer' thing will be a girl-centric threesome with one harem girl, the MC, and one girl not yet in the harem. There aren't feelings, only sex. It will be the possible door for the second girl to enter the harem. Obviously, if the lesbian content is blocked, it blocks also that girl. And even with the lesbian content unlocked, the player can decide to not pursue that threesome.