Spoilerrrrr
Basically shushu's ex was also liu's ex(not like they were serious tho only fbuddy ish). Shushu dated that man for 3 years(very serious about him even provided his stay abroad) than found out he was cheating (he was the bottom oop). So his old injuries relapsed while fighting with the ex. Liu thinks if he told shushu how he dated him and how he is is hardcore bottom (shushu is an omega and he isn't into topping) then maybe they wouldn't have fought and he wouldn't need to stop his passion for dancing. So he is more caring towards shushu.

Was there ever anything between Shushu and the ML? And if not, why was he so rude to the MC in the beginning?