#or Celestial Realm somehow resists her omniscience.

[villain-in-love]

Okay, I like this maker. Here, ladies and gentlemen, we can see young Belial hitting on Simeon:

I think when Belial and Simeon first met they were still teenagers by demon/angel standards.

It was a diplomatic trip that the Devildom's royal family (consisting of the Demon King, Diavolo and Belial) took to the Celestial Realm. For Belial, Simeon stood out to her as one of the youngest angels amongst his rank, and she immediately got captivated by his mischievous smile and intelligent eyes.

They both understood that she used her status as a royal guest on a diplomatic visit to approach him so that he wouldn’t be able to turn her down, but Simeon didn’t mind either way. He was curious too. Belial, delicately avoiding the sphere of politics and geography, asked many questions about the culture of the Celestial Realm and what it's like to be an angel, along with some more personal questions about Simeon himself (What does he think about humans and their world? Does he actually like the life of virtue? What are his hobbies? What kind of literature does he like to read?) Simeon, on the other hand, was interested in what life was like for a demon and carefully listened to all the comparisons Belial makes between Celestial Realm and Devildom, sometimes asking for details about what it’s like to be a royalty in hell and, by the way, how often does she visit Human Realm? Just asking because maybe they could meet again sometime…

But honestly, at this point other angels weren't even surprised that Simeon befriended a demon.

And that was the start of a millennia-lasting friendship that may have started with mere infatuation but grew to later become an actual romance.