Mitsuya Souma, a first-year student, has spent his whole life with his decisions made for him by his mother, who seeks to protect him from past family tragedies. He finds solace and freedom only by playing the violin gifted to him by his bed-ridden grandfather, Yoshimitsu. Yoshimitsu's days are now almost over, and one night, the dreaded phone call comes in of his sudden decline in health. At the hospital, Mitsuya gets into an argument with his mother, only to be cruelly interrupted when an earthquake hits the city. Mitsuya falls down the stairs, hits his head, and passes out.

Upon waking up, Mitsuya finds himself transported back in time to the Taishou era, surrounded by his grandfather's family and friends. Confused and struggling to cope, he concludes that he must correct his grandfather's biggest regret. However, Mitsuya has no idea where to begin. He must find his way amid a developing relationship with Jin Kasuga—his grandfather's best friend—and increasing family drama.