Complex sentence: Ironically, Rin's hidden desire is to be a singer like his late mother but decided to give up his dreams because of his bad voice, which was often referred by his schoolmates to' resemble the voice of a dying frog'.
Split into simpler sentences: Ironically, Rin's hidden desire is to be a singer like his late mother. A desire he had buried a long time ago because of his bad voice, which was often referred by his schoolmates to' resemble the voice of a dying frog'.