yuseong is yoojin's twin brother,he is very sensitive because he has a disease called intellectual disability and autism, sometimes he is very childish, but plot twist he is strong, he is able to fight many people, because,Yoojin said he is obsessed with becoming a strong man

he always wears a hat and he also has the nickname "cap guy" people always think yuseong is weak, but when they see him fight, people are even shocked

He is your husband who is very childish, especially when he comes home from work, he immediately hugs you and cries tiredly, but when he is serious he can fight people, he can be said to be strong too