Yandere female uppermoons and muzan x male reader

Yandere's personality and past

Muzan:

Personality: cold-hearted, ruthless, intimidating, and exceptionally intelligent. But gets really happy when talking to y/n and loves him very much. Believes him to be the perfect man for a queen like her and wants to be the perfect wife for her darling, and have kids with him.

Past: she was the only daughter in the Kibutsuji family, their family was very rich and had two kids one of them being her younger brother and the other kid being herself, she was cursed with a disease that would have killed her at the age of 18.

She always acted monotone and didn't care about anyone after she found out about her disease and always tried to find a way to cure herself so she could live longer and had developed a fear of death. her parents still didn't know about the disease and wanted to get her married in the future in a rich family like theirs and because she was the older one of them she had to get married first only then the younger one could get married and become the heir of the Kibutsuji family.

They often made her meet with random boys that were from rich families and tried to make her become friends with them. But muzan already knowing their intention always refused and just walked back into her library to find a cure for her disease, but one day her mother came to her and took her to meet with another one of those random Boys, she was ready to just refuse them and then go back to her library. But then she saw him. She couldn't describe just how beautiful.......... just how perfect he looked. She was mesmerized after looking at his heavenly-looking e/c eyes. And she didn't hear any of them except for him. Again being fascinated after hearing his voice full of excitement as he introduced himself as a name that she'll never forget. Y/n l/n. After that, they Played for some time and she actually felt happy being with him and smiled and felt sad when he left with his parents.

Her parents told her that they live nearby and he'll visit here to play with her everyday. She was beyond happy to hear that and had decided that he'll be the one she'll marry. But then she realised that her disease would kill her and won't let her be with her beloved, this made her carve for the cure even more than before. After years her feelings for him only grew but her disease got worse so she had to get visited by a doctor who couldn't recognise the disease and just passed It off like a normal disease. But her condition only worsen to the point they had to go to C/n to visit a famous doctor.

She was sad that she'll have to leave y/n for such a long time but if she could be cured and live the rest of her life with her y/n then it was worth it. When she became a demon she went back to her beloved's house after killing her parents and the doctor but when she returned she saw the house old and a bit broken down when she asked the nearby villagers they told her that his parents had died and it was still not known what had happened to the Boy but they said that he was also most likely dead. Hearing that she killed all of them in rage and then held the locket he gave her tightly. But she didn't believe he was dead........there was no way he could have died. She simply refused to believe it. After all, he promised to meet her again and the villagers said it was still not known what had happened to him. Yes, he has to be alive. That was what she thought at that moment. After that, she started to go around the country in search of her beloved and wanted to get the blue spider lily to become the perfect being and an immortal so she could search for him even in the sun. She also started to create more demons in hopes that one of them would find the blue spider lily or become immortal so she could devour them and become immortal.