I kinda smelled this twist coming the second it was revealed he had a brother with which they had a bad relationship, but I didn't actually expect he fucked his brother's wife.
And yeah that's all I have to say. Worse yet when he's apparently more successful than his brother, being a consultant for a foreign company and all, I can only hope he got his nuts kicked out once before by Tesshi...but he reeks of a gaslighter (I mean, look at what he did to poor Kuon), so likely he just put the idea into Tesshi that he was fully at fault for being consumed by his own worries.