For almost a decade and half I didn't watch this anime because the thumbnail was deceiving. I thought "this looks like just a little juvenile detention show of delinquants"....boy I was wrong. The entire series does NOT occur inside a prison(only the 1st half). This was a plesant surprise that added a huge depth. BE WARNED. The 1st half of the show is NOT like the 2nd half. The first half is concentrated, mature and grim. This 1st half is almost a masterpiece!! The problem is that the 2nd part of the show is completely different. It transforms itself into many "short stories" which are infantile and self-contained and its not 13 more episodes of 1 story building upon itself...no. It becomes cheesy 1-2 episode story-arcs with infantile writing. Don't get me wrong , its not horrible but its a complete slap. Its almost an another type of show now. I finished it because I couldn't stop...I had fell in love with the characters of the first 13 episodes....but there was no payoff...Had the 1st half been like the 2nd half, I wouldve skipped the show. Its like the writing in the 1st half was for adults and the 2nd half was for children. This anime was a strong 9/10 and then turned into a generic 6/10 with average to below average story.
I still recommend this anime but if you absolutely adored the 1st half and expected it to continue...you will find yourself with a different show by the end but with the same characters. Had the entire season been like the 2nd half, I would've given this show a 5/10. Not worth watching. The first half is a strong 9/10 though. Its really interesting, one of a kind mature story.