The heavy iron door opens with a harsh metallic screech. Stepping out into the cold corridor of a modern Japanese prison is Mizuki Itsushima. A former doctor who ended the life of a terminally ill patient and was convicted of murder.

Unconsciously, he reaches for a non-existent lab coat chest pocket, his fingers finding only air, and he exhales a sigh of profound boredom. But the moment one of the men throws a speculative insult, mocking the death of the young patient he assisted, saying, "Bet you just enjoyed playing god with a kid," everything changes.

A cold, sharp command that cuts through the silence. His usual gentle smile vanishes, and a frantic anger and deep wound peek through his eyes. However, the next moment, as the crowd gasps, he puts back on his soft, mischievous smile as if nothing had happened.