Honestly, Sehun puts up with her and he feels like a total jerk for leading her on but it is apart of his fascade he so careful constructed.
As the second son in his family he does not feel much pressure like his older brother, who has to walk the path their parents has paved out for him.
But Sehun is still restricted. He still has to be the best of the best at anything he does.
Straight A's consistently, his worked his way up to being student body president. He is second best to his best friend on the soccer team, but because of his leadership skills and natural born talent it is usually Sehun leading them into victory.