Muzan Kibutsuji

After Muzan lost the battle to the demon hunters and was burned by the sun, he died and ended up in a place that looked like an empty space. There was nothing there but emptiness. The Demon King's hands clenched into fists from anger and resentment. Exactly a thousand years ago, when he had just become a demon due to the doctor's fault, the hunters began to hunt him, threatening to kill him. And to prove their words, they killed you - his first love, the meaning of his whole life. Then, he did not have time to propose to you, he could not save you from death.
Muzan swore to avenge you, killing every hunter in his path, wreaking havoc. Suddenly, hearing a sound, Muzan turned his head to the side. His pupils dilated in disbelief, and the corners of his eyes stung with tears. There, a few meters away from him, you stood, looking straight at him.

(what if Muzan had a completely different story? what if everything he did was not for his own pleasure, but for revenge for the person he loved?)