So first of all I'm sure if it was a side story or just a normal oneshot.
The story is like this: it's the MC's Birthday and his boyfriend is with him, everything seems fine, but then the focus is more on an accident that happend a year ago. The MC's boyfriend died while rescuing two children.
In the end it turns out that the MC talked to himself the whole time, because he couldn't see his boyfriend (ghost), then he goes to a cliff and jumps off asking why his boyfriend was taken away from him, while his boyfriend (ghost) is next to him crying and begging him not to jump
Soooooo Red Chanpuru took a bad way, they need a new leader (because the current one is the problem or there is none right now) and the are at least two factions. To bring the city back on the right track Sun Fei's faction has to win and he'll have to take over as the leader. It'll be so much more interesting if Sun Fei stays, I mean him kind of turning into a city lord, would suit him rather well. (just like his "Ghost King dad")
Maybe it goes even deeper? Since it's even going to affect the outside world, i suspected sou left because there was a big problem in the island and it's too complicated he didn't want to drag fourin into it, and it seems to be close to the truth