Harukanaru Toki no Naka de is a Japanese shojo manga series written by Tohko Mizuno who also worked on the video game of the same name, which was developed by Ruby Party and published by Koei. The manga was serialized in LaLa DX magazine from July 1999 to January 2010, and published by Hakusensha in 17 volumes.
Although an exact time period is not given for Akane’s arrival in Heian Kyou, it seems likely that the story is set in the earlier part of the era, when families such as the Tachibana-ke, Fujiwara-ke and Minamoto-ke were all in some prominence. Though the Fujiwara-ke and Minamoto-ke continued to hold significant position through until the Genpei war, the Tachibana-ke faded out of favor during the 9th and 10th centuries. This suggests that Harukanaru Toki no Naka de is set sometime in the 9th or 10th centuries. This would also fit with later continuations of the Harukanaru Toki no Naka de plot, since Harukanaru Toki no Naka de 2 is set a century later, and features prominently once more the Fujiwara-ke and Minamoto-ke, as well as the Taira-ke. The third installment, Harukanaru Toki no Naka de 3 is set in the period of the Genpei War, which came to an end in 1185. If it can be considered that the third installment is set a century on from the second, this would indicate that the original Harukanaru Toki no Naka de storyline is most probably set in the latter half of the 10th century.
On her walk to school, ordinary Kyoto High school student Motomiya Akane hears a voice calling to her from an old well in an abandoned historical estate. The voice is that of the oni leader Akuram, and Akane finds herself summoned into another world that resembles the city of Kyoto during the Heian Period (approx. 800-1200). Here she is asked to be the Ryuujin no Miko, a legendary figure who possesses the power of the gods. Akane is told that she must defend this world, called Kyou, from the encroachment of the Oni Clan before she can return home. Fortunately, her school friends Tenma and Shimon are on hand to help her out and along with six Kyou natives they become members of the Hachiyou, a group of specially chosen men who act as the Miko’s protectors.