beta
im currently reading the novel and little sejin really grew on me. he's actually a sweet hyung but his conflict with big sejin is actually because he thought big sejin hated him cuz he's more of a hard worker than a talented person so when they practice he's a bit slow than others. he thinks big sejin hates people with no talents hence why he's always sound sarcastic or fake to him. and big sejin didn't like him because he think little sejin is not professional(like he obviously show he didn't likes him cuz big sejin can fake his likeness so why can't you). but also because his past when he's pushed out of the debut line last minute cuz of that guy parents is an actor. like he unintentionally got a grudge against actor
well that's my understanding though not sure how others interpret it