Six former classmates meet at their high school reunion: legal secretary Tamaki, businessman Takumi, single mother Yuka, shoe salesman Taichi, tech CEO Shoji, and teacher Moe. As their conversation turns to long-ago loves lost, Yuka makes a shocking confession: in the summer of their second year, she lied to keep Tamaki and Takumi from getting together! After a night of drinking and reminiscence, Tamaki awakens to find herself ten years in the past, on the day that fateful summer began. But just as she learns Takumi has returned to the past as well, they both receive a mysterious text message... Those life-changing summer days have come around again, but can the past truly be changed?