From what I see, sister is manipulative, she was also the reason why these two fought, what if uke wanted seme to know what kind of a person his sister is, she didn't care about his brothers life and it was always about herself.
I'd say sister is more at fault than uke, for me uke is using this as opportunity to get seme for himself.
Sister is a bitch, okay! But MARRIAGE?? Dude should've said NO. That's it. Uke is a psycho.
Let's wait for more chapters to see what made him say, yes when he first rejected her.
Uke is fucking wrong for that!!! Why marry his sister?
The fuck! Even if she's the one who push for marriage, HE COULD'VE SAID NO AND FUCK OFF FROM HER LIFE!!