"Muzan-sama, may I enter?" As Muzan was laughing like a madman in a very quiet voice, he suddenly heard a very feminine and gentle voice calling him from outside the sliding door of his room.
"You may," Muzan quickly composed himself, not wanting anyone to think he had gone mad before he even became a demon, lest he be burned alive.
Though Muzan was quite confused about who this voice belonged to, the maid had mentioned that the doctor, who was trying to cure Muzan, had concocted a cure and was here to administer it.
Soon, the sliding door opened, revealing an extraordinarily beautiful sight. Before him stood a woman with long black hair and purple eyes, dressed in Heian-era doctor's attire.
She was truly stunning; to put it in perspective, she could easily rival Hinata or Hanabi from Naruto and Mitsuri from Demon Slayer in beauty. She appeared to be in her early twenties, precisely 21 years old.
"Who are you?" Muzan asked, his expression filled with confusion as he locked eyes with the woman before him.
Hearing this, the woman frowned slightly before saying, "Don't tell me the last medicine affected your memories." She moved closer to Muzan and began to massage his head.
"What are you doing?" Muzan tried to push her away, but to his surprise, he couldn't muster the strength. Despite feeling weak and pathetic at the moment, he couldn't understand why he couldn't push away a freaking woman away.
"Muzan-sama, it's me, Hiruma Hatsumi, your doctor," Hatsumi said with a smile, continuing to massage his head.
"My doctor?" Muzan fell into deep thought after hearing these words from Hatsumi before yelling in his mind, "DON'T TELL ME I REINCARNATED INTO SOME SHITTY AU!"
Muzan was convinced he had ended up in a terrible alternate universe. He distinctly remembered that the doctor treating him wasn't a woman so beautiful she could have stepped out of a Disney princess movie.
Instead, his doctor was an ugly, old man.
"Muzan-sama, have you truly lost your memories?" Hatsumi asked gently as she continued to massage his head.
It was something she did almost every day when she administered her experimental medicines to help keep Muzan calm.
Losing his temper could lead him to harm her or anyone around, as he had already killed dozens in fits of rage.
Even then, finding the cure for Muzan's mysterious disease was very difficult, and no matter how many medicines Hatsumi made, they always carried the risk of side effects like memory loss.
But she wasn't going to give up on Muzan. To say she had a crush on him was an understatement—she was madly in love with him.
She was just like Hinata from the Narutoverse, but Hatsumi was even more obsessed. She loved Muzan so much that she would kill anyone who tried to harm him.
"Fuck... now I don't even have any advantage in this world," Muzan thought, as Hatsumi pondered ways to restore his memories.
If this world was an shitty Au, Muzan couldn't rely on his knowledge of Demon Slayer canon, as many things might be different in this world.
Since if this world is au, then muzan can't really rely on the information he about the canon of demon slayer, since many things might be changed in this world.
"Muzan-sama, can you tell me how much of your memories you've lost? Do you remember nothing at all, or just parts of them?" Hatsumi asked, her purple eyes focused intently on him.
"Well, I still remember my name and my disease... I think I just don't remember you," Muzan replied. As soon as he said this, Hatsumi's demeanor changed drastically, resembling Hashirama from Naruto in a state of instant depression.
"What does he mean by he doesn't remember me? Damn it! Does he even know how much I've sacrificed for him? I might have sacrificed more than his parents, and he says he forgot about me? This is all so messed up," Hatsumi thought, her internal monologue filled with frustration.
"Muzan-sama, since you remember your disease, you must also remember that you will die the day you turn 20 if you don't take the cure. For that, you must trust me," Hatsumi said, taking out a bottle from her bag.
"Ah! The medicine made from the Blue Spider Lily," Muzan thought excitedly. This world might be an alternate universe, but this scene was familiar to him.
It was the moment when Muzan took the medicine that transformed him into a demon. This event seemed to be a fixed point in both worlds, a canon event.
"Muzan-sama, what I have here is a medicine I made with the help of many elders from my clan," Hatsumi began to explain, holding the bottle carefully. "Though it's just a prototype, I am confident it will cure you."
She hesitated for a moment before continuing, "However, it might have some side effects. So, I want to ask you if you still want to take this medicine or not."
"Yoriichi, you can suck my dick this time," Muzan thought, a dark glint in his eyes as he stared at the medicine. In his mind, he was already imagining how he would finally defeat and torture that Yoriichi, the source of his past trauma.
Despite the PTSD Yoriichi had caused him, Muzan was determined to dogwalk him this time—at least according to his own deluded confidence.
"Wait a sec! I don't need to fight that son of a bitch," Muzan thought, a sinister smile spreading across his face. "I'm in the Heian era. I'll just kill that son of a bitch's ancestor."