Do you think Shin really lost his mind?
Since we all know that Maya has the Amaterasu Gate and it's heavily hinted, but not proven that it might be the reason why Shin wanted to stick to Maya so much, do you think he was just trying to save everyone else from himself by keeping everyone else (especially Mitsuomi since he loves the girl and would've taken her away if things didn't go the way they went) away from her? All I can say is that the closer and closer he got to his death, he became more and more protective of her. Shin saw himself being killed, but maybe he was trying to break himself from the Wheel of Fate before it was too late. Although Mitsuomi was the one who "killed" Shin, if Maya had the gate back then, everything that happened because she didn't intervene theoretically could have been avoided.