Koyuki Honda, like many of her classmates, looks forward to her graduation ceremony. Unfortunately, unlike her peers who have family to attend, Koyuki has no one left besides her deceased brother. While visiting her brother's grave, she crosses paths with two brothers named Kiri and Victor Putin who are chasing after a peculiar creature. Initially assuming they are actors filming a movie, Victor captivates Koyuki with an age-old legend about the cemetery's clock tower: if someone makes a wish under it during a full moon at midnight, time will rewind, and they can reclaim what they have lost. Koyuki decides to make her wish, but instead of fulfilling her dreams, she uncovers a horrifying truth. The clock tower legend is a ploy created by time-stealing demons called "Horologues." As Horologues are drawn to regrets, Victor uses Koyuki as bait to lure a demon. Kiri and Victor reveal themselves as Chronos Rulers, skilled warriors who use the "Oath of Time," an item that can manipulate the passage of time, to fight against Horologues. After defeating the demon and preventing a crisis, Koyuki is free from her regrets and can move forward. But there are many other people out there with similar sorrows. Kiri and Victor must continue their fight against the Horologues in order to protect humanity.