From Chibi Manga:
Yukari and Haruhi are the same age while Ruka is 4 years younger and they are all childhood friends. The three of them get along well with each other, but unexpectedly Haruhi confesses his love to Yukari and the two begin dating. But, Ruka forcibly chases after Yukari causing her heart to wander between Haruhi and Ruka. Although she doesn’t want to break up with Haruhi who is nice to her, she can’t stop the heat that she feels when she is with Ruka… The everyday peaceful life has turned into a continuation of storms!