Look through the thread, it's all explained. Long story short, though: the (very male) MC can change into a female version of himself in order to seduce, corrupt, and conquer lesbians into his harem. He also creates a familiar, who is a younger succubus-like girl who is also kinda part of him. You switch to playing the familiar for a few segments of the game, and seduce, corrupt, and conquer girls into the MC's harem/ISPOILER].