MC's GF is an idol. He discovers his gf is doing "favors" to the boss and other high profile old men to further her idol career. It starts as a blackmail by the boss by showing her a picture of MC and her together, threatening her that as an idol, if the photo "leaks" and the public learns she's dating, her career is over. So she starts doing sexual favors. What I don't understand is the MC discovers her cheating on an online board. The boss is uploading her videos there and she knows that she's being recorded, which is worse than her photo with the MC spreading. It's unclear to me if she knows it's being uploaded online since I'm just skimming throughout the game. Anyway, MC unlocks cuckold fetish and jerks off to gf's sex videos. Ironically, a photo of her and the boss going out of a hotel (or in?) spreads in public and they were forced to lay low for a while. MC uses this opportunity to confront his gf about her cheating. Then he reveals to her his cuckold fetish. After this, there are 3 choices accompanied by cgs of its own and leading to its own endings. (1) You stop the boss and beat him up, which leads to the idol company shutting down due to bankruptcy. Gf gets mad, becomes femdom and pegs the mc, training him to become submissive. It is implied that they will get married and the mc will suffer eternal pegging. (2) You embrace the cuckold. You finally get to join your gf getting gangbanged. (3) You proposed to the boss to pretend nothing happened and keep doing their cheating. Boss tells your proposal to your gf and she reads through you. Time skip, she video calls you while having sex with the boss, you ask questions like what she's doing and she answers in seducing sexual innuendos that turns you on. This is now your daily life. Everytime she's doing it with the boss, she calls you to tease you but not outright tell you since all three of you are pretending nothing's going on.
As far as I know, no bad ending where they separate. The end.