I wonder, what kind of ending Link Click is going to have?
On the one hand, there is a possibility for sad ending. From season 1 we hear over and over the same mantra: you can't change the past. It's very dangerous for the whole universe, so you must accept what happened and move on. Also, there are hints that everything is already predetermined by fate, and noone can change it. So, why is Lu Guang going to be an exception and why Cheng Xiaoshi will be allowed to live? It's possible that the moral of whole story is: you have to accept that even the closest people in your life die, and you have to move forward. Still, it's hard to imagine that Lu Guang will live happily without Cheng Xiaoshi, even if the finale shows us that he will move on.
On the other hand, if we look at the anime series about time-travel, most (if not all) of them have a different idea: you can change the past. Fight the tragic destiny, and everything will be fine. You don't have to accept the "inevitable" tragedy, instead, if you fight for happy future (with friends by your side), all deaths will be avoided. So, maybe Link Click wil have the same conclusion? Also, Cheng Xiaoshi had so much character development, moreover, he found friends who love him. The whole meaning of the show is friendship between the main trio, so I don't see the point in separating them. Yeah, of course, in real life this happens, and you can't bring people back from the dead, but I don't think that's how THIS show is supposed to end. So, maybe, Lu Guang will have to ask for help from Cheng Xiaoshi, and that's the point of the show? That you don't have to deal with everything alone, or something like that? And in the end Cheng Xiaoshi and Lu Guang will stay alive together?
And here comes the third option: bittersweet ending, which is more likely possible. If you think about it, every clients' story ends on a bittersweet note: sad events happened, time had passed, but in the end there's some happiness. So, what if Cheng Xiaoshi stays alive, but he will not be allowed to befriend Lu Guang? And Lu Guang, knowing this, will stay out of the way, so the tragic events won't happen? Or maybe Lu Guang will sacrifice himself for Cheng Xiaoshi's life, but the latter won't even know it, because he'll, I don't know, lose memories about Lu Guang. However, again, this donghua shows us the importance of friendship, so, in my opinion, it would be very cruel and hypocritical to separate the main characters.