Sukuna does die in the manga. The way it happens is quite dramatic and ties in with many other elements of the story, adding depth and tension to the overall narrative.
One possible story could be that Mimiko is bitten by a mysterious vampire one night while walking alone. She then starts to experience strange cravings and enhanced senses. At first, she's terrified, but as time goes on, she begins to embrace her new vampiric nature.
Yes, there might be. There are many fanfic communities out there where such stories could exist. You could try searching on popular fanfic websites like Archive of Our Own or FanFiction.net.
No. Ryomen Sukuna is a fictional character from Japanese mythology and modern manga/anime. He doesn't have a basis in a true historical event or person.
Nope. Ryomen Sukuna has no basis in reality. It's a product of the creative minds of the writers and illustrators who designed a captivating fictional character for the enjoyment of the audience.
A great aspect of this fanfiction is the world - building. The Black Blood Brothers universe has a lot of potential for expansion. Writers can create new factions or powers that Jiro and Mimiko have to deal with. This not only makes the story more engaging but also gives a fresh perspective on the original world.