Jing Yuan and Xing Yue backstory is not similar/same as Tian Qi and Yuemi in ALP. So you can really treat Moonlight Mystique as a standalone.
While I did like Tian Qi and Yuemi's backstory in ALP, I have come to really love Jing Yuan and Xing Yue as a pairing and their backstory in Moonlight Mystique (as a standalone).
And because I love Jing Yuan and Xing Yue as a pairing, I just want to shed some light (from my perspective) on how I tried to cope with their ending.
The below will contain spoilers, so if you don't want spoilers, then feel free to exit out this thread.
*** SPOILERS BELOW ***
Jing Yuan and Xing Yue have a bittersweet ending. Jing Yuan loves Xing Yue and he did said he desperately want to see Xing Yue again.
At first Jing Yuan saw Bai Shuo is Xing Yue because she carried Xing Yue's divine mark, but didn't want to admit that Bai Shuo is not Xing Yue since Xing Yue is dead and its too painful for him to accept this fact.
Bai Shuo is Xing Yue's reincarnation and Bai Shuo is herself. She's not going to be Xing Yue because she's not.
How Jing Yuan was able to awaken after 60,000 years later into Fan Yue's body was because he used his Divine Power(which can be like a part of his soul) to bind the hidden heart back then so a part of his remnants still exists in this world that was binded to the Hidden Heart. When Bai Shuo used the sword to attack Zhen Yu and injured the Hidden Heart, this sets Jing Yuan free where he was able to enter into Fan Yue's body and awaken as Jing Yuan.
For me, Jing Yuan and Xing Yue back story is truly tragic. They wouldn't have gotten that tragic ending back then if Heaven Fate(Tian Dao) didn't forbid Xing Yue from being with Jing Yuan. But honestly, without the tragic backstory, there would not be the Fan Yue and Bai Shuo that we came to love.
I know it hurts Jing Yuan to accept that Bai Shuo is Bai Shuo and she's not Xing Yue anymore. Because that is him acknowledging that Xing Yue is no longer in this world.
Jing Yuan truly loves Xing Yue and just like how Bai Shuo cannot take Jing Yuan the same as Fan Yue(because Bai Shuo only loves Fan Yue), the same is with Jing Yuan because he only loves Xing Yue. He accepted they are two different people.
The moment he accepted that Xing Yue is no longer in this world, my heart 💔 goes out to him, because that's when he decides to join her(Xing Yue) in the stars. I like to believe that he did find her again(as we can see the two stars join together) and they have reunited in the stars. Jing Yuan was selfless when he decide to give the body back to Fan Yue and that did make me love Jing Yuan better too 😭😭
In the overall, how I took the theme to their backstory and ending is, Fan Yue and Bai Shuo are reincarnations to both Jing Yuan and Xing Yue, and they lived on as their happy ending. Just like what Jing Yuan said to Fan Yue before he joins Xing Yue in the stars: that perhaps his awakening(60,000 years later) was to give them(Fan Yue and Bai Shuo) a chance to be together. He told Fan Yue to protect Bai Shuo well and don't let their(Jing Yuan and Xing Yue) regrets in the past repeat itself 😭😭 so to me, this is how I saw it... To say I am not sad would be a lie, because I was sad in that scene, but when I look at this in another sense/perspective, their ending gives a sense of bittersweet where their happy ending lives on in their next life(as Fan Yue and Bai Shuo) it actually makes sense if you look at reincarnation side of things. I felt like how the writers wrote this was very poetic and sad, yet beautiful in a way, that the love they held for the one they love is irreplaceable. We saw this through Fan Yue, Bai Shuo and Jing Yuan.
So in the end, does this make me dislike Fan Yue and Bai Shuo? No. Because Fan Yue and Bai Shuo deserves their happy ending too and considering all their suffering and sacrifices they earned it and I am glad one way or another Jing Yuan and Xing Yue can live on in Fan Yue and Bai Shuo in that sense(in the next life).