Inside Mari Vol. 7 by Shuzo Oshimi

A college student apparently wakes up in the body of a high school girl.
There is no turning back now, "Mari" has said good-bye to the person she knew as Isao Komori. But now this Mari must fully commit and accept the past of the body she inhabits. That includes the pain and the memories the Yoshizakis have been suppressing for years.