Rainbow: Nisha Rokubou no Shichinin

Synopsis

The seven boys have become comrades and spend time working out in their cell. Joe reveals that he has a younger sister on the outside. Seeing her again is his sole motivation to endure the school. Joe later receives a visit from the orphanage administrator where his sister is staying saying his sister is about to be adopted. Afraid he will not see her again, Sakuragi and the other boys cause a distraction allowing Joe to escape through an unguarded entrance. The boys are beaten and placed in solitary confinement. Turtle recounts losing his entire family in the atomic bombing of Hiroshima and why he helped Joe escape. Joe arrives at the orphanage and attempts to escape with his sister but is caught by the police. Joe's sister 'rejects' him and sends him away (in an attempt to protect him). Distraught, Joe is returned to the school and placed in solitary.

(Source: Wikipedia)