Lol... yes. That maknae is "head over heels" for BoA... He loves BoA to death, I bet... hahaha. Besides being a fan of BoA, I'm also a fan of EXO.. xD
I heard from my friend that Sehun and Luhan were not originally choosen to dance and collaborate with BoA for "Only One". It was their fellow member from EXO-K. Kai. But as soon as Sehun knew it, he begged his manager to exchange places with Kai. After much begging, EXO-K's manager gave in and gave him permission to have the opportunity to dance with her lovely sunbaenim. But the day that he had to go the rehearsal room to meet her for the Only One dance, his legs failed... (lol.. I know I might sound mean... but please... little maknae was nervous and that's hilarious xP) he had to ask Luhan for help to accompain him, maybe for moral support, I think.
To resume it, maybe BoA took notice of Luhan too, and decided in the end that both Sehun and Luhan will dance with her.
If you had seen the performances where Sehun appeared, you will notice how serious he was. My friend told me, due to the fact that he admires a lot and it was BoA's comeback, getting this lovely opportunity to dance with her, he wanted to do his best and not fail her.
I think that's very sweet of him. The only "issue" I have about him, it's that I hope he stops being shy and nervous around her. Since BoA is very nice and funny, if he keeps like that, she might have a heart attack if he suddenly faints in front of her... LOL... xDD
Even Shindong told him he was being so greedy about that... xDDD He reminds me of Yuhno when he brags about having danced with BoA... xD