Reviewers highlight the stark contrast between the "Seinen" brutality of the prison setting and the "Shounen-esque" idealism of the boys' friendship. It is often described as a story about finding hope and a "ray of light" in a dark, incarcerating world.
The new boys are stripped, beaten, and thrown into their cell. That night, something unexpected happens. An-chan, the oldest and most enigmatic of the group, begins to hum a melody. He asks Mario if he knows the song. Mario recognizes it as —a popular post-war folk song about freedom and flying away from sorrow. rainbow nisha rokubou no shichinin chapter 1