The Girl Who Leapt Through Time

is a science fiction novel by Yasutaka Tsutsui. Originally serialised in seven installments in two of Gakken's secondary school student-aimed magazines, beginning in Chūgaku Sannen Course in November 1965 and ending in Taka Ichi Course in May 1966, and first published as a book in 1967 by Kadokawa Shoten, it has gone on to become one of Tsutsui's most popular works and has been reinterpreted in other media many times, the most famous internationally being a 1983 live action film directed by Nobuhiko Ōbayashi and a 2006 anime film directed by Mamoru Hosoda. The original novel was first published in English translation by the British publisher Alma Books on May 26, 2011, in a translation by David James Karashima.

The title is also that of a song, written by Yumi Matsutōya to be performed by Tomoyo Harada for the 1983 film, which has enjoyed considerable fame of its own.

Plot
Kazuko Yoshiyama, a third-year middle school student, is cleaning the school science lab with her classmates, Kazuo Fukamachi and Gorō Asakura, when she smells a lavender-like scent and faints. After three days, strange events transpire around Kazuko, including the burning of Gorō's house after an earthquake. The next morning, at the exact moment of a car accident, Kazuko is transported 24 hours into the past.

She relives the day and relates her strange experience to Kazuo and Gorō. They do not believe her at first, but they are convinced when she accurately predicts the earthquake and ensuing fire. Fukushima, their science teacher, explains Kazuko's new ability as "teleportation" and "time-leap". To solve the riddle of her power she must leap back four days.

Finally, Kazuko's determination enables her to make the leap. Back in the science room, she meets a mysterious man who has assumed her friend Kazuo's identity. He is really "Ken Sogoru", a time-traveler from AD 2660. His intersection with the girl's life is the accidental effect of a "time-leaping" drug. Ken remains for a month, and Kazuko falls in love with him. When he leaves, he erases all memories of himself from everyone he has met, including Kazuko. As the book ends, Kazuko has the faint memory of somebody promising to meet her again every time she smells lavender.

Other Sources

 * Fansite for the 1972 Time Traveler TV series adaptation
 * Review of Toki wo Kakeru Shoujo (Portuguese)