One possible plot is that a young and inexperienced heir is sitting on a throne. They are guided by a wise old advisor, but face challenges from ambitious nobles who want to usurp their power. The fanfiction could explore how the young ruler grows in wisdom and strength, overcomes the challenges, and earns the respect of their people. They might start by making small but important decisions, like improving the living conditions in the poorest parts of the kingdom.
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.
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.
In the manga, Sukuna doesn't possess all 20 fingers. There are specific story arcs and events where his finger count changes based on the plot developments.