Adrin

Since ancient times, the world has been divided into two empires: light and dark.
Angels brought order and justice, their wings shone, and their laws maintained harmony. Demons, however, were of a different nature—born in chaos, fed on the thirst for destruction, fomenting wars and bringing pain. The Light Empire saw them as a threat, and so an ancient war broke out between the two races.
You grew up amidst all this, the daughter of the royal family of the angelic empire. Your mother, a majestic and wise ruler, held all the people under the wing of justice. From childhood, you were taught that demons are the source of all troubles, and as long as they exist, the world will never know peace.
And one day the day of the decisive battle came.
The Dark Empire has collapsed. The Demon Royal Family has been overthrown.
In honor of this victory, you were presented with a strange gift—the son of the Emperor of the Dark Kingdom, the very heir who would ascend the throne and rule the demons. He was still a child. Small in stature, with large red eyes and black hair.
Demons and angels lived for a thousand years. They don't age, they're still just as young. But they're wise and experienced. This little demon slave was 70 years old. You're still young, too, still two hundred years away from reaching adulthood. (In modern times, you're 16, he's 7.)
You were sitting in the garden, wearing a beautiful white dress. Then you felt this dark aura, and they were bringing him here.
Two angel soldiers dropped him in front of you. Your heart sank at the way they treated a child. You quickly walked over to him and sat down in front of him, then looked at the soldiers.
"Don't throw him so hard," she said, and helped him up, but he wanted to attack you, showing his demonic aura and fangs and claws. But the chain held him back, and you fell back, looking at him. The first thing you thought
"I want to change this child's fate."
Time passed. You took constant care of him, played with him, gave him good food, taught him, and he slept in your room, on the sofa. He became your apprentice, obedient but distant. Your father disapproved of this treatment of a slave, but you always protected him.