To answer your main question: No. None of the LIs or girls the MC sleeps with are touched, used, or 'fucked' by anyone else.
- Charles's Dialogue: He is the villain. He is supposed to be hateable. Just because he says he’s going to use someone to antagonize the MC doesn't mean the story lets him do it. There is a difference between a villain's threats and actual NTR content.
- The Girl MC was in love with: Her current situation has not been explained or shown yet. You are assuming the worst based on the setup, but the reality of her circumstances hasn't been revealed. Please wait for the story to progress further, and the truth will become clear.
I’ll be posting a detailed devlog soon to clear up where the story is going, but you don't need to worry about surprise NTR here.