
Possible Spoilers....
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It might have something to do with the Seme's older brother (who is the "Perfect" angel of the family and why his mother/grandmother (not sure) always puts Seme down).
In the raws, it looks like the older brother sexually and mentally abuses him (he notices uke likes him. They are about the same age while future Seme is much younger, probably 12 at the time) while uke is living in their home when they were teenagers. The Seme, while a still child, develops love for uke but uke doesn't see him that way and doesn't notice the crush (I don't think - he seems detached at this point since Seme's older brother is abusing him).
Uke seems to develop either self loathing and a fear of commitment as many of his partners wanted to have serious relationships with him and he couldn't do it.
He keeps finding faults in his partners so he can dump them and if they want him seriously he leaves them faster.
I don't think Seme knows about abuse from his brother. He was aware that Suha was interested in him when he was a kid and probably takes it as reinforcement that his older brother is always preferred over him.

Also....
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Sorry, I forgot this the Seme's mom, who is the president of the company, now wants to transfer Suha (uke) to be the secretary for the older brother.
Umm...Why is the uke so slutty? ( ̄へ ̄)