Kimi wa Yoban me

A young man named Shii woke up to find himself in a body he didn’t recognize. According to the doctor, he is the fourth of several split personalities to form within this body. Before the brain succumbs to the strain of housing these multiple identities—causing all of them to vanish forever—Shii is tasked with identifying the "original personality" so that he may eliminate the "fake" personalities, including himself. Will Shii be able to restore the true personality to his body? [Translated from Novelgame]