Min Hyuk
1) because poor boy already fall for Bong Soon so much since episode 1
2) he is supporting her, helping her, caring for her
3) he is accepting her they way she is - she doesn't have to pretend being someone else, he accepts her, her weirdness and powers as one, as integral part of person called Bong Soon.
I know for now Min Hyuk - Bong Soon relationship looks more like "2nd lead relationship" and Gook Doo - Bong Soon like "1st lead" (aka she loves him, admires him but he doesn't really return the feelings yet - while MH already fallen for her, helps her, protects her, thinks about her, but yeah she doesn't noticed it - typical 2nd lead thing...).
But I hope it will change soonish XD
PS. tell me, is it too much? should i put spoiler tags? :S