It's been a long time. Can someone please remind me why Yo du is so angry at Qi an?

I honestly don’t even think the author has explained that in the story yes ┑(￣Д ￣)┍

Kian left him 5 years ago. Parents dead through car accident, promised to be by his side forever, broke promise. Ta daaa

Dropped out of school so he could work to pay dad’s hospital bills. But for some mysterious reason felt it was better to disappear and abandon his good friend in his time of need, cause he didn’t want his friend offering to help him.

Well that's stupid and disappointing. But it seems Yo Du isn't aware of these circumstances, which you'd think with his money, power and connections he would have found out already....