
I have a question. Didnt hayato's father agreed to their relationship in prequel of this manga?? Then why he'll kill them knowing they're in Japan?

If I remember correctly, his father wasn't going to consent it first, but when Hayato spoke his feelings and intentions towards Shirou he let then leave and both of then decided to go travel and be together. But Tsukiya is not the only one with power in the clan and we can't forget that Shirou used to lead the rival faction that kidnapped Hayato... so the other branches couldn't possibly have a good opinion on it. I hope the child will be okay and we can have a family together ending, considering the danger they find themselves in to right now.
Not just ex.. This seme is also no good. Seme rudely telling uke that its just physical relationship, don't talk personal matters and all... then mr.rude-ass seme don't ever come after uke and persist when you finally catch feelings for him.