This drama starts out a bit confusing, but in a good way, and by the second or third episode, you figure out what is going on, which sucks you deeper into the drama's plot. Honestly, this drama deserves a 10...right up until the last ten minutes or so of the last episode. Since endings are so integral to the experience of drama watching, I had to deduct a half of a star for two reasons (spoilers ahead):

One: We never get a clear resolution to what happened to the young version of our killer. While Chen Yan Ru lives on, so does our child psychopath serial-killer-in-the-making. Did his family get him the help he needed early on, or did he keep on killing cats until he escalated to murdering humans? While it is clear having his older self possess his big brother's body and teach him how to kill fueled his murderous desires, he was already on that path to begin with, so resetting the past wouldn't clearly put the killer-to-be on a new path to redemption. But if this unresolved plot-line somehow opens the door for a sequel where Xie Zhong Ru still becomes a serial killer in the new timeline and coincidentally sets his eyes Huang Yu Xuan as his next victim, I'm here for it because...

Two: We do not get a nice wrap-up to Huang Yu Xuan and Li Zi Wei's romance. Yes, we're left with enough that we "know" that they will end up together somehow, but I want to know how. Did Li Zi Wei somehow keep in touch with the young Huang Yu Xuan, who fostered a crush on him for years until one day he eventually saw her as a woman and feel kind of skeevy about it because of their age difference, or did he randomly run into her on the street when they were 28 and 38 and mistake her for his childhood friend Chen Yan Ru? I just wish the ending had been: young Huang Yu Xuan and Li Zi Wei on moped, followed by a montage of Huang Yu Xuan and Li Zi Wei meeting and dating in the future, that then transitions into older Yu Xuan and Li Zi Wei riding on the moped.

Overall, though, this is an amazing drama, one of the best I've ever watched. I just wish the ending had been as tight as the rest of the drama's storytelling.