Man. It's been so long I can't remember if she's the dense type or not.
Either way, Maisen for the assist! He seems to be the "flirt" in this otome, so it's just as well he goes to the dance with her.
I realize that he's the main romance, but I still find it somewhat...uh...unpleasant? Unpleasant when love interests act possessive. Jealousy is normal, but there's a line to be had. Then again, I guess Mr. "never thought of her as my sister" didn't really have a normal childhood.