Rainbow ~ Abe George (Story) & Kakizaki Masasumi (Art)
Summary from mangatraders:
Just finished the first volume and it really is an awesome Manga.
Six minors (16 to 17 years old) answering to the nicknames of Joe, Mario, Suppon, Baremoto, Biceps and Cabbage are put into a reformatory for offenses such as aggravated assault, swindle, flight, etc. Their stay in hell begins immediately. Accommodated by a doctor pedophile, they are placed under the monitoring of a despotic and brutal crew. Companions in the cell of Sakuragi (called Anchan), the tension flares up between the band of buddies and their new "friend". A brawl breaks out and our six prisoners are done rossés by mysterious young man thanks to his boxing talent.
The story will not only follow the lives of these seven characters surviving in their hellish environment, but also their disillusions due to the rejection by the outside world and by their close relations. This is about the extraordinary and invincible friendships between these young men.
You can read it here.