Cheng Fenghui (Joseph Cheng) appears at the most depressed time of Su Ying (Claudia). Su Ying finally couldn't resist his eager pursuit and accepted Cheng Fenghui's proposal. However, just as Su Ying was about to have a flash marriage with Cheng Feng, Su Ying began to receive all kinds of strange information photos and other clues from a "mystery man". Out of curiosity, Su Ying began to investigate through these clues, and finally came to a creepy conclusion-Su Ying's fiance Cheng Fenghui turned out to be Lin Qiang, her classmate who died in a strange fire in high school 15 years ago. The youth of more than ten years ago reappeared in Su Ying's mind with her in-depth investigation. Fifteen years ago, the sunny and confident teenager Jiang Zhongyun (Beom Kim) walked into the heart of the same Su Ying. A very pure and beautiful first love began like this. Like all first love, Jiang Zhongyun and Su Ying shared all the good times of their youth. But the difference is that Su Ying found that Jiang Zhongyun often silently protected and took care of himself in the dark, and never admitted that he had done these things. Su Ying was deeply moved by this effort of asking for nothing in return or even knowing you. Such a big boy who is always sunny and can stand up silently at critical moments has become a solid support for Su Ying. The two decided to go to the same university and meet a better future together. But just before the college entrance examination, a strange fire broke out in the school chemistry laboratory. A charred body and a broken student ID card at the scene of the fire confirmed the death of Su Ying classmate Lin Qiang. But Jiang Zhongyun seems to be a different person after the fire. ...