A cute established relationship story with a monster of the week plotline.  They're a sickeningly sweet couple and nothing happens to rock the boat there.  I did find a bit of boredom in the chapters that revealed their incredibly long past history but it was mainly because the MC lost a lot of his more mischievous and fun characters to fall back on the trope-y sweet and innocent shou personality.  I got a kick out of the extras about them as high schoolers though.
I was totally cheering for Rong Yu as Ace King of Universe, considering the man noped so hard of getting into a relationship that he became a defector from his world and a demon just to avoid having to follow his plot. 

I will continue to headcanon him as asexual for the rest of my life, even if he did eventually get into a relationship with Yan Zhao