When Haru Kaidou rushes to Canada after hearing his mother is gravely ill, he discovers a surprising twist—his mother's health scare was a ruse. Not only that, he finds himself tasked with caring for Ren Kaidou, his adopted brother who prefers the company of canines to humans. Despite Ren's initial wariness, Haru perseveres in building a bond with him. They forge a pact to reunite in Japan post-Haru's graduation. Tragically, an accident erases Haru's memories of their shared summer, including their vow. Years later, a hopeful Ren shows up in Tokyo, only to encounter a Haru oblivious to their past, dismissing him as a stranger.