Enter a bloody cycle of fate deep under the ocean. Will you become everyone’s salvation? A train shuttling underwater carrying students and teachers on a graduation trip is suddenly trapped in a strange time loop, endlessly experiencing the moment of a derailing accident . . . Our protagonist WuShi and his friends are onboard a highspeed rail train, which is a tourist attraction that goes through the belly of the sea. What they do not know is that once upon a time, the train is a vehicle for time travel experience.The joyful journey quickly spirals out of control when the train derails, locking everyone in the moment of the bloody incident that endlessly repeats itself.WuShi happens to be the only person that remembers each and every fateful cycle. But what’s even stranger — with each repeating cycle, one more of his classmates dies before the train’s derailing moment. A mysterious murderer has appeared, and in the name of deliverance hunts down and kills Wushi and his friends . . .Ren: Male protagonist.He loves railroads and trains, especially the epoch-making undersea broad gauge tourist train "Time Journey".He has a straightforward personality and up to two friends. He has grown up with Cecilia and Sol since childhood. No matter what happens, they would face everything together and solve them.Cecilia: A childhood friend of Ren, she has a therapeutic personality. Her dream is to start a beautiful and ordinary family.Luna: The sole heir to the Cesium Corporation. Also the inventor of the time machine during the time travel on the undersea railway.She is beautiful and is versed in both literature and military affairs, but under the perfect appearance, there seems to be a hidden side.There was a rumor on campus that she was conducting some kind of grisly experiment using humans.Denes: The personal maid of Luna. Also an underclassman of Ren, Cecilia and Sol by one year. Will do anything for Mizuki, even if it means sacrificing her own life. Seems to have experienced something in her life, making her expression always Sol: A friend of Ren and Cecilia. A star player of the school basketball team. Has a very robust build, but seemingly not too much of a ladies’ man. Always confused about the subtle relationship between Ren and Cecilia. Half of it is out of worry, and the remainder is frustratedly watching over the two of them. S: ???