I don’t know, but could the skateboard mean that Nanjo is the one or gonna leading the relationship? He put one foot on it, so maybe it could symbolize, “I’m taking that step, and I’ve got this.” And it’s also pointed forward, forward mean “keep going” or in this sense “keep moving forward on to the relationship”
Basically he is da boss and mokyeon is a manchild
No offence to you mok, you are cute, but you are really giving bottom vibes right now