Hero's Path: Riku confesses his secret to Mio and ends the relationship so she won't fall into the abyss along with him. He starts dating his older and more mature cousin, and they manage to understand and solve their problems together, living a happy life.
The Path Meguru Ueno (Author) will take: The cousin will never appear again, and he will stay in this push-and-pull dynamic with Mio until the manga gets canceled. Around chapter 100, horny ghosts from Riku's ancestors will start showing up, trying to hook up with him. One of these ghosts will possess Mio and try to do the same, and it will be up to him and Akeno-san to get rid of the lustful ghosts.