It was actually the father that said his sphere was tainted because of sensei. I've come to the conclusion that Ryuu-Oh is an idiot and a drama queen.
oh his father said it? i must have mistaken him for the sensei xD and indeed, he is a drama queen (≧∀≦)
I thought his sin was maybe that even though he's in love with sensei he married and slept with someone else... Like his sin was his betrayal. Cause his chi only got tainted later on... But that's just my theory ╮(￣▽￣)╭
i thought so too.
so on this page http://www.mangago.zone/read-manga/binetsu_kakumei/an/binetsu-kakumei-chapter-2.html/58/ I think the sensei contradicts himself? he says that outa has the power to purify chi...but then he talks shit and says that tatsuki's sphere would be tainted because of his homosexual relationship with outa..... like what?!
so the sensei uses outa to purify tatsuki's dad's sphere that was tainted because of his homosexual relationship with sensei.....BUT if outa purifies chi, then tatsuki should never be tainted in his relationship with outa right?......
i may have interpreted that wrong so correct me if i am wrong. but i still think the sensei is stupid to blame tatsuki's father's condition, on their past homosexual relationship...i really don't like the sensei, it was their own bad judgments and actions that lead to that negative consequence...but the sensei is not really taking responsibility and just sort of black mailing outa to fix his mistakes!!!! like seriously! some adult he is!