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.
One common theme is the exploration of morality. Meruem's own moral compass is complex, and in crossovers, it gets further explored when he interacts with different characters from other universes. Also, friendship or rivalry is a big theme. He either forms new alliances or makes new enemies in these crossovers, which drives the story forward. For instance, in some fanfictions, he has to decide whether to trust a character from another world or not, which adds a lot of depth to the story.
One great 'Meruem x Reader Fanfiction' is 'A Meeting of Minds'. It really delves into the complex relationship between Meruem and the reader. The way it describes their interactions, from the initial curiosity to a deeper emotional connection, is really engaging.