Responses
HeTian was unaware of the damage his disappearance did to Mo... Mo didn't know if He Tian would return, he probably hid everything that reminded him of Tian in the box so as not to be saddened by old memories.
I remind you that the plot of 19 days is that He Tian and Jian Yi disappear for several years from the lives of Mo and Zhen Xi, and reappear in their lives when they are adults with jobs and careers (=・ω・=)
Wait why he's sad I'm confused