Nezu, Jouji

Joe is the sullen oddball of the five boys, who struggles to fit in outside his group of friends (and sometimes within). He suffers from a bloody cough due to severe stomatitis, though the disease is neither chronic nor physically debilitating to him. However, his canker sores do affect his speech, with bloody coughs often punctuating his sentences and interrupting his speech. Despite being the quietest, Joe is actually one of the more lecherous of the five, reflected in the crass way he speaks and makes jokes.

Joe also has a love and appreciation for ants to add to his quirks, going so far as to name the ones he keeps in his ant farm and being able to tell them apart , though they all look alike. Towards his friends, Joe is shown to be accepting and supportive.

Though he initially shuns Kiyoshi after he learns of his escape, Jo returns the kindness shown to him after Kiyoshi prevents him from assaulting the USC president. Due to being the last of them to have spoken to a girl out of the five boys, Jo enters a depressive phase after being freed from prison. As a result, he decides to attempt returning to the Prison Block out of loneliness as the other boys are enjoying their freedom. However, his outlook on life in the school improves when he meets Satou

(Source: Prison School Wiki)