The pocket watch explained

the pocket watch is a symbolic gift from Kim Dokja to Yoo Joonghyuk, created by Aileen to represent the concept of time and a promise for the future, encouraging Joonghyuk to live in the present world despite his regressions. It symbolizes their bond, with Joonghyuk cherishing it like a wedding ring, but later becomes the focal point of their major conflict when Joonghyuk leaves it behind, signifying a potential break in their shared path