In "Golden Days," first-year student Mitsuya Souma lives under the strict control of his overprotective mother, who dictates every aspect of his life due to past familial tragedies. His only refuge is playing the violin, a gift from his ailing grandfather, Yoshimitsu. As Yoshimitsu's condition worsens, a distressing phone call alerts the family to his critical state. At the hospital, Mitsuya clashes with his mother until an earthquake disrupts their argument, causing him to fall, hit his head, and lose consciousness. Upon waking, he finds himself transported back in time to the Taishou period, among his grandfather's relatives and companions. Confused and struggling to adjust, Mitsuya resolves to rectify his grandfather's greatest regret. However, he faces the challenge of navigating this unfamiliar era while developing a relationship with Jin Kasuga, Yoshimitsu's closest friend, and dealing with mounting family conflicts.