Pharmaceutical researcher who secretly develops a time travel formula. After a car accident leaves her in a coma, she briefly regains consciousness to instruct her daughter Akari to travel back in time and deliver a message to her first love. Her past time-traveling experiments indirectly shape the events in 1974.
Kazuo is Kazuko's lost first love, whose past promise drives the time-travel mission.
Kazuko's daughter travels back to deliver a message to Kazuko's first love, Kazuo. Kazuo later tells her about his history with Kazuko and the promise...