Hana to Ryuu

At seven years old, Ryuji's yakuza parents were murdered in front of him, leaving him so traumatized that he erased the memories from his mind and started living with his new mother, his biological aunt. At seventeen years old, Ryuji comes home one day to find his unknown past had caught up to him. While ten years ago his mind protected him by forgetting, now his body protects him by fighting blindly until nothing was left but dead bodies, pools of blood, and... his little brother Tomoya. What further hell awaits him in prison...?

(Source: Fantasista)