I don't think the mc is a succubus or a hybrid, she is simply a human who made a contract with a succubus, and she transformed her body by changing her sex and improving it by giving her a charm that can attract both men and women, and when The more excitement he receives, it seems as if his connection with the succubus is maximized, so far a slight change in eye color can be seen.
At the moment I don't think he will have both sexes but who knows in the future
, and as for his mind, it is clear that little by little he is changing or that is what I have seen without playing the recent update.