Demon Slayer + Katekyo Hitman Reborn
Unfortunately, the serum didn't work on Nezuko, why, no one knows, but the serum worked on Tanjiro, everything is according to the canon except that Nezuko remained a demon, they tried to develop a new serum, but to no avail.
And so, standing in front of her brother's grave, and comforting his wife, Nezuko decides to leave so as not to cause any more problems. For a while, she lived with the second surviving demon, Yushiro, but soon left him. While traveling, Nezuko meets a foreigner, from whom she learned the language, and after that she got the idea to visit his homeland. Nezuko Kamado ceased to exist at the age of 27, and Limera Blair appeared.
(If I'm not mistaken, Nezuko was turned into a demon in 1912, she was 12, so she was born in 1900, and left Japan in 1927 or 1928. In 1939-1945, she observed the war, but did not interfere, only if it concerned her safety)
Just traveling around the countries, she did not notice how 1981 came, noticing this fact, Limera decided to stay in this country for a while, Italy is really a beautiful country.
One day, while walking through a random forest, Limera came across a boy with a sword, he was strange, and Limera involuntarily remembered the times when her brother was still alive, there was something familiar. Out of curiosity, she began to follow him. Limera often noticed him next to another guy, he had a similar feeling to her brother. Only more violent, more powerful, something that makes you want to appropriate yourself, something that makes you want to bow your head. Without realizing what she was doing, Limera made an "offer" with that purple fire that used to glow pink. She was noticed then because of this, but after so many years, she doesn't regret it a bit. After all, this is her Sky.
• After Nezuko left Japan, she changed her name, and for the first three years she was with the foreigner who taught her the language.
• Nezuko became an active flamethrower on the mountain with the spider family, but before the fire had a pink hue. As you understand, Nezuko, or rather Limera, is a Cloud, the Cloud of Xanxus.
• Tanjiro was the Sky, but too soft for Nezuko, so there was no Heaven/Guardian bond.
• Limera sometimes ate people, but only then could she not recover with sleep.
• Varia knows that Limera is not Italian, but no one knows which country she is from, they found out about it only a couple of days before the conflict.
• I really like the idea of the Hibari clan practicing cannibalism, I would like to see this in the work. I would also like to see Kyoko and Kei's friendship.
• Limera fights without weapons (mostly with his feet), and if he needs them, he just grabs whatever comes to hand, be it a stone or a person.
• When Limer was returned to Japan for a while, she visited the graves of her family, and after that Yushiro, where they had a conversation.
• Limera, Keya, and Kyoko have become friends to some extent, and sometimes they do things that make you want to hang yourself, the rest
• Varia is totally crazy, but the family
° Tanjiro's wife, this is Kanao.
° Nezuko never responded to Zenitsu's advances.
° I believe that all hunters who have awakened the marks will eventually die at 25.