Gareki no Rakuen

A lawless investigator enters a prison island and encounters a clever, bold boy with an unsettling aura. A decade later, the boy, now named Yuuto, lives and works with Shigure, the man who saved and raised him. Yuuto has long concealed affection for Shigure, and his repressed emotions have made him increasingly volatile. His feelings eventually lead him to wish for death in Shigure's presence. What seems like an opportunity arises during a chaotic street gunfight.