On the night of a crimson full moon, Ayazuki Mei, a female high school student, is enticed to enter a magical box by a mysterious magician named Charlie. When she awakens, she finds herself in an unfamiliar park. Unable to fully grasp the situation, two handsome men appear before Mei, Mori Ogai and Hishida Syunso. She does as she's told, and rides in their carriage with them and finds herself at the Rokumeikan, a luxurious Western-style house from the Meiji era, at a party with high-ranking officials in attendance.

During the party at the Rokumeikan, Mei is treated like a suspect by a police officer named Fujita Goro, but Ougai pulls her close and calls Mei his precious fiancée. Having no place to go, Ougai brings her back to his mansion and tells her that she can stay until her memory returns. Mei is being toyed with by Ougai's gentle alluring words. Meanwhile, Syunso, who is a freeloading art student living at the mansion as well, seems to be troubled by something putting him in a poor mood.

Now that it is clear that Mei is a Tamayori who can see ghosts, she decides to help Syunso find the black cat that became a divine spirit and left his painting. While conducting their search, Mei and Syunso happen to run across Koizumi Yakumo and Izumi Kyoka and Yakumo asks Mei for her help in investigating some paranormal happenings at his hotel. The ghost, it turns out, is likely a childhood friend of Yakumo's. Ougai is against the investigation out of concern for Mei, but she insists on helping regardless.

Ougai openly admits to his aunt, who has brought him photos of possible marriageable young women, that Mei is his fiancée; and, he also states his intent to formally present her as such at a party being held at the Rokumeikan the following month. Sensing Mei distress at this, Ougai invites her out on a date to Asakusa. After being escorted around Meiji era Asakusa, Mei seems to brighten in spirit. However, while out on their date Mei is faced with a beautiful girl who clearly is one of the hopefuls for Ougai's hand.