Responses
I also think it’s because of yujins personality though, he’s been shown to have a fear of commitment. He's always a free spirit. So when things got too serious with Aaron and he started feeling something for him, he ran away.
*also a free spirit
Is yujin's main concern that he's afraid of what his dad will do to aaron? Is that why he left? To keep him safe? They should just communicate that to each other.
I'm sure aaron has more than enough resources to fold his dad like a lawn chair if need be.