Manticore: Seishin Ikou Jikkengai

University student Mimi Usazaki spends her days battling depression while attending psychiatric sessions and muddling through a bleak college life. One fateful day, she's caught up in a mysterious experiment that alters her life forever. Through the experiment, she ends up hosting the consciousness of Hyou Usazaki—her estranged younger brother, who also happens to be a death row inmate. Now, Mimi finds herself thrust into a deadly struggle against other death row inmates who were subjected to the same experiment. Will she survive the chaos that ensues? Or will her connection to her brother bring about her downfall?

(Source: MangaDex)