This animation series is based on the hit comic "Rainbow - The Seven Boys of Dorm 2, Cell 6" which was serialized from 2001 in "Weekly Young Sunday" published by Shogakukan. It was one of the most popular stories in the weekly magazine and received the prestigious Shogakukan Manga Award in 2005. The manga itself has 22 volumes which have collectively sold more than 3.3 milion copies as of March 2010.

The story is set in the 1950s, a time when Japan is still suffering from the effects of WW2. Mentally hurt by the war, many young men turn to crime and are scorned by society. This story focuses on six junior delinquents and their mentor at the Shonan Special Reform School near Yokohama. The delinquents, who answer to the names of Joe, Mario, Suppon, Baremoto, Soldier and Cabbage, are befriended by their older cellmate "Anchan." They form a close bond as they together face bullying by their Reform School mates and abuse by their doctor. In this hellish environment, they still dream of getting through these rough times and finding a bright future. What the delinquents don't know is that the world which awaits them outside the reform school is more harsh a reality than they expect.