Mihane can't wait to enjoy her last summer vacation in high school. One day, she smells the scent of lavender in school and collapses on the spot. On her way home, she realizes that she has acquired the ability to travel freely through time.

Nishioka tells Mihane that his personality changed after receiving a heart transplant. Mihane is interested in Nishioka's donor and decides to travel back to meet the girl who will be Nishioka's donor.

Mihane regrets that her class did not present anything at the last high school festival. When she learns that Shohei and Goro feel the same way, she decides to time travel and make a proposal to her classmates.

Mihane and Shohei begin dating, but Shohei is worried that his secret will be out. Meanwhile, Goro runs away from home, unable to bear the expectations of his parents. Mihane and Shohei try to stop Goro by time traveling.

Miura, who is from the future and realizes that his own mortality is imminent, asks Mihane to do him a heartbreaking favor. He further tells her that Shohei is from the future and that Shohei has been rewriting the memories of Mihane and the others.