Lost Youth summary: “Is there any purity in this tangled friendship and romantic relationship?” Aine Misabashi, a cheerful second high school grader, has a massive crush towards her popular childhood friend, Riku Shirota. She also has a beautiful best friend, whom she calls as "Princess" that always listen to her insecurity. Everything seems like an ordinary innocent youth drama until Aine saw Riku kissing another girl even though he always said that Aine is the only one he has. Moreover, the girl that he kissed is... Is there any purity in this tangled friendship and romantic relationship? What will Aine do when another important person to her also has a feeling towards her...?