I saw this on Netflix and assumed - incorrectly - that it was associated with another recent Chinese movie on Netflix I'd seen, Ne Zha. That one was set millennia ago, this one is set in a steampunk 1930s fantasy China. I found out they weren't associated (except for being based on the same myth), but kept watching mostly because of the aesthetic, which is ... amazing.
As a movie, it's pretty cheesy: young man races motorcycles and acts as a courier for a courier service of questionable legality in a (fictional) city called Donghai that's sorely short on water. He's rebellious and breaks the law, but has a heart of gold. It turns out that the city (and particularly the water) is controlled by the De Clan, who are actually a family of immortal and evil dragons. But our hero is the reincarnation of Nezha, and as he learns his powers, he goes to war fighting injustice.
The plot isn't very good, but I found it worthwhile because of the interesting and lovely artwork.