The most interesting thing about Ash and Yut-Lung's relationship to me is the potential that never got realized and the regrets that may come from that.
They were so alike and could have helped each other but that didn't happen. Instead Yut-Lung teamed up with Dino and tried to ruin Ash's life out of petty jealousy. And I have a lot of sympathy for Yut-Lung and I know why he logically would choose to side with an already established powerful person if he wanted his brothers out of the way, and I know how his bitterness toward Ash and Eiji comes from how hurt he's been in the past. But he still did those things and kept going after Ash despite how he'd done basically nothing to him.
And the thing is that Yut-Lung gets to survive. He has Sing who cares about him and wants him to do better. And I wonder if in the future, when he's older and a potentially more sensitive person, if he has regrets. Does he think about how he could've had someone else who would understand him and maybe even care about him? Does he regret burning that bridge before he even noticed it was there?
Simply put, so much could have happened but none of it did and that's the tragedy of it all.