Responses
It had to do with his father. Yujin was afraid his father would hurt Aaron, so he ran away for his sake, thinking he'd be saving him then. Cause Aaron got his brakes cut off and got into a car accident, and yujin knew it was his dad
Guilt..Yujin's dad tried killing Aaron; also his mom mistook Aaron as his son and was killed in an accident while chasing after Aaron. So guilt and a bit of resentment. But mainly guilt. And also to protect him from his father as he tampered with A's car recently
why yujins running away