--Humans grow cat ears when they fall in love.
In this world, when you fall in love, you grow cat ears. Fujise, a handsome prince who is the most popular boy in his grade but who thought that serious love was irrelevant, discovers that Kirigaya, a serious member of the library club, has cat ears. He wonders if Kirigaya also suffers when he thinks about the love of his life, even though he doesn't seem to be in love with anyone. One day, Fujise sees him crying outside the school building, and for some reason he thinks that Kirigaya has beautiful cat ears, and is moved by this...?
――ヒトは恋をするとネコ耳が生える。この世界では恋をするとネコ耳が生えてくる。学年一モテるけど、本気の恋なんて無関係だと思っていたイケメン王子の藤瀬は、マジメな図書部員の桐ヶ谷にネコ耳が生えていることを知る。恋なんてしなそうなのに、桐ヶ谷も愛しい人を想って苦しんだりするのだろうか。ある日、校舎の外で泣いている姿を見た藤瀬は、なぜか桐ヶ谷に生えたネコ耳がきれいだと思い、心揺さぶられて――？