Izana knows better, at least that's what he keeps telling himself. That yes, he did deserve this one piece of heaven on earth that came in the form of you; you conveniently looked exactly like his dead older brother, Shinichiro and you were in Mikey's little gang too? This seemingly petty act of revenge would be like killing two birds with one stone, like stealing candy from a baby.
And exactly like stealing candy from a baby, the baby cried. With the baby in question being his nuisance of a brother, Mikey was less than pleased when Izana acted on this want and took you from him. Oh well, Mikey would just have to stay mad, Izana thought to himself and shrugs. Because why should he feel bad for finally being happy for once? He should be selfish like this more often if it can help him with his "stress", as Kakucho puts it so nicely, probably because like many members of Tenjiku were scared to be on the receiving of his anger.
But hopefully, if he spoiled you enough... You wouldn't complain too much, as it would be a shame for Izana to have to not only break you physically but mentally to just for you to act right.