Six students must face different lessons in love — a love closer than they ever imagined, a love they must run to catch up with, and a love that returns carrying an old promise — before they can grow, hearts and all, through "LOVE×3 The Mandatory Love Course." X1: The love story of a high school boy secretly in love with his best friend — only to be roped in as Cupid, helping him woo someone else. X2: The love story of a senior student council president who must win the heart — and the LINE ID — of the school's most adorable underclassman star. X3: The love story of a younger student bound by an old promise, secretly in love with his own brother's best friend — keep waiting, or let it go?