Bi Yuechen woke up to find that she had transmigrated to the System's cycle of reincarnation.
The System told her there was no way back. Her only requirement was to keep peace among the Three Realms, after which the System would never come looking for her again. She had three choices:
A. Start with an egg
B. Choose to be human
C. If you don't choose, you'll be an animal
The difference between A and C was that the egg contained Bi Yuechen, the young lord of the Demon Realm.
In the Demon Realm, women held power. Forced to become an egg, Bi Yuechen was raised beside Feng Guiyin, the daughter the Demon Lord had brought home a thousand years ago.
After hatching, she stayed by Feng Guiyin's side constantly. When war broke out between the gods and demons, the Demon Realm won completely, and the pure and chaste Feng Guiyin was to marry the Celestial Realm's God of War. Bi Yuechen returned from the front lines gravely wounded, nearly going berserk.
She spent days and nights taking Feng Guiyin by force.
Bi Yuechen: That's it? And you call yourself pure and chaste?
Feng Guiyin disappeared without a trace, and peace returned to the Three Realms. Bi Yuechen was punished by being sent to the mortal realm to undergo tribulations. She resolved to keep her heart still, but then met a fairy who looked just like Feng Guiyin and was herself taken by force.
Feng Guiyin: That's it? And you call that keeping your heart still?
War broke out between the gods and demons again. This time, the Celestial Realm won completely. The Celestial Empress Feng Guiyin avenged her past humiliation, the Demon Realm was utterly defeated, and it teetered on the brink of collapse. Bi Yuechen, who had barely had time to settle into the role of Demon Lord, was sent to Feng Guiyin by everyone.
Bi Yuechen: Before, peace among the Three Realms came first, then love. Now, only love can bring peace to the Three Realms.
This is a melodramatic story. That's all I've got for now, but I'll revise it later.
Theme: My fate is mine to decide, not Heaven's.