Plz help what anime is this?

i cant think of this animes name and its killing me i remeber its about a boy and a girl and they transform using some sort of rings. in one episode the dude acts all weird then he kisses her. and then they have a senpai who is a girl but crossdresses as a guy. then main girl always wheres her hair in 2 ponytails and the main guy charecter is blonde. i no for a fact the anime starts with a k but i just cant think of it.