In the bustling halls of Tokyo's Kuranose High School, 17-year-old Makoto Konno finds herself drawn into an extraordinary adventure when she discovers a cryptic message on a blackboard. This marks the beginning of a remarkable journey that will radically transform her life. After a serendipitous encounter with a walnut-shaped object, she suddenly acquires the unusual ability to time-leap, enabling her to traverse through time and space. In her quest for understanding, she confides in her aunt Kazuko Yoshiyama about this incredible phenomenon.
At first, Makoto revels in her newfound powers, using them to manipulate her circumstances. From skipping tardiness to effortlessly acing her exams, she makes the most of her gift. A memorable karaoke session becomes an endless delight as she relives those joyous moments repeatedly. However, as her escapades advance, she comes to realize the unintended consequences her time-leaping has on those around her. Her heart grows heavy with the awareness that her actions can disrupt the lives of her friends, including her best friend Chiaki Mamiya, who faces an awkward romantic disclosure.
In a bid to rectify the chaos she has caused, Makoto sets out on a mission to mend the trouble her whimsy has wrought, all the while mindful of a mysterious numbered tattoo on her arm that indicates the dwindling number of her time-leaping opportunities. As Makoto nears the end of her time-leaps, she is faced with the urgent responsibility to amend her past mistakes. Just as she gears up to make amends, Chiaki reaches out to her, prompting her to use her very last leap to avert the call.
Meanwhile, Kōsuke Tsuda and his new girlfriend Kaho Fujitani unwittingly take Makoto's faulty bike, completely unaware of the peril that awaits them. In a bold move to save them from an imminent train collision, Makoto finds herself unable to intervene, her reserve of time leaps completely depleted.
In a twist of fate, as despair looms large, Chiaki reveals himself to be a time-traveler from the future. He freezes time, guiding Makoto through a now-still city, and discloses that the walnut-shaped object is his time-travel device, which he had used to leap back and observe the restoration of a painting by Makoto's aunt Kazuko. With clarity unfolding, Chiaki confesses that he has exhausted all his time leaps and will not be able to return to his timeline. As he shares this revelation, he also asserts a heartbreaking farewell, aware that their lives are now eternally intertwined.
As the clock resumes ticking, Makoto is left with a whirlwind of emotions. Initially overcome with grief at Chiaki’s sudden departure, she soon finds determination filling the void. In an unexpected turn, she learns that Chiaki's time-leap has reset, transporting him back to the moment just before her initial foray into time travel. Seizing this chance, Makoto deftly utilizes the restored device to leap forward in time, arriving precisely where her journey began.
Now armed with fresh insights and a determined spirit, Makoto aims to protect the restoration of the painting, hoping to ensure that Chiaki can experience its beauty in his time. Before he departs again, Chiaki leaves her with a heartfelt promise that he will be waiting for her in the future. As he dissolves into the fabrics of time, Makoto returns to her present, where Kōsuke inquires about Chiaki. With a knowing smile, she reframes the truth, suggesting that Chiaki has embarked on a new academic journey abroad. As the curtains draw on this chapter of her life, Makoto embarks on her own path — one brimming with hope, promise, and the thrill of new beginnings.
