Psycho no Sekai

A girl is murdered and her body severed, but the killer remains unidentified and the case fades from public memory. In a society where the powerful dominate the vulnerable, her childhood friend, Mamoru Inubo, waits twelve years before seeking vengeance. Determined to punish the perpetrator ignored by the world, he starts preparing for retribution by seeking a long-missing ally. He embarks on a challenging path to fulfill his plan.