Ōgai Mori met Osamu Dazai at 14 years old in an asylum when he took him in as his patient who had recently attempted suicide. On the same night, Mori murdered the dying former Boss of the Port Mafia whose only aim at that time was more death and destruction with a young Dazai as his only witness. Mori found the child disturbingly similar to him in nature, and, as a result, a competent right-hand. Mori soon manipulated young Dazai to join the mafia.

Mori cares about him and sees him as his son.