Five years ago, Sasakura Mizuki was caught in a flood at the Shiroyu River and rescued by a young man.

And now, Mizuki suddenly receives an offer of marriage to that young man—Tatsuki Shingo.

Though suspicious of the mysterious proposal, Mizuki accepts due to her feelings for Shingo and family circumstances. The wedding will be held at Ouryu Shrine, where the Tatsuki family is a parishioner.

However, on the day of the ceremony, Mizuki is murdered by someone.

The dragon god enshrined at Ouryu Shrine appears before her.

The dragon god, who has descended for the ceremony, is said to be able to return Mizuki to the time before she got murdered.

The special sake Mizuki drank at the ceremony apparently makes this possible.

The dragon god resides in the Shiroyu River, where Mizuki once drowned.

Though filled with mixed emotions, Mizuki asks the dragon god to turn back time.

Along with the dragon god who for some reason accompanies her, Mizuki sets out to find her killer in order to avoid death.