Responses
I think that he explained why. He was just a coward. He didnt want touma and his family to suffer from going against the girl. I also think thats what the letter he had sent was for. To explain that no matter what hed love him and that he would always but things are happing that made him have to marry her. I agree that is kinda shitty of him to just leave Touma hanging and that, although a bit extream, toumas reaction was understandable with the lack of context he had as to why he was left by Hayato.
Hayato could’ve told Touma why he was getting married. Just because he got blackmailed by the girl claiming to be in love with him he didn’t have to hold to her demand to keep the conversation between them. It makes sense that touma held a grudge so strong he wouldn’t let any reincarnations of himself be happy with hayato’s reincarnations. After all he ended himself full of heartbreak over being abandoned. Reasonable crashout.