The noble Mo He accidentally fell from his horse, allowing another soul from the distant future to take advantage of the opportunity. But that soul forgot its original self and completely integrated into Mo He's life. Except for feelings, of course.
Seventeen is reborn at the beginning of all stories with memories of his previous life. He didn't think about how to change, but the result was obviously better. He couldn't forget the person he fell in love with, and he became the only one in his eyes.
To put it simply, it is a story about time travel and rebirth. It's just that the person who traveled through time doesn't remember what happened before he traveled through time.