I need to go back and read some chapters again because I’m so confused
Hajin learns about the twin chapter 18. Chapter 19, He was told the twin was the teenager Hangyum he knew from the past. But the idol is really the teenager from the past. Hanwool as Hangyum meets Hajin for the first time in chapter 27 and 28. Chapter 39 is when Hajin is meeting Hanwool as Hanwool. Hanwool is being so dodgy because he pretended to be the Teenager Hangyum that knew Hajin in chapter 27 and 28. Here he is being introduced as Hanwool and exposing Hangyum's lies.
I love the slow burn of this story... A lot of stories just rush into the romance and sex stuff