It's possible that some new characters are introduced in this fanfiction. They could be powerful underworld figures that Naruto has to deal with. These characters could have their own motives and backstories, and they would interact with Naruto in various ways, either trying to ally with him or overthrow him as the king of the underworld.
Well, it could be about Naruto ruling the underworld with his unique ninja skills. Maybe he uses shadow clones to manage different aspects of the underworld, like keeping the peace among different criminal gangs or uncovering dark secrets.
The following were some recommendations for novels that were similar to the King of the Underworld: " Don't Run, Hades "," The Concubine of the Underworld "," Hades in Power: A Dainty Wife Can't Escape "," Hades Chases His Wife: The Useless Second Miss of the Underworld "," The Snake of Hades "," The Strongest Killing God of the Underworld "," The King of the Seven Realms "," The Heart of Hades "," The Emperor of the Underworld Surrenders, the Concubine of the Underworld "," The Concubine of the Underworld ", etc.
One common theme is the exploration of a new world. The underworld in Naruto fanfiction is often a mysterious and dangerous place. So, Naruto has to explore it, learn its secrets, and find his place. Redemption can also be a theme. Sometimes Naruto tries to redeem characters from the underworld or even the underworld as a whole. And of course, friendship. He makes new friends in the underworld, which is different from his Konoha friends, and these relationships help him in his adventures.
In some fanfictions, there might be Naruto - related shops near areas that could be considered 'underworld - like'. However, it really depends on the creativity of the fanfiction author. Some might create such unique settings for the sake of plot twists or to introduce interesting new elements into the Naruto universe within the fan - made story.
Maybe through a series of unexpected magical events. For instance, he could accidentally stumble upon a powerful ancient magic in the Forbidden Forest that has a connection to the underworld. This magic could bind him to the underworld in a way that gives him the position of king. Or perhaps he is tricked by a dark wizard who wants to get rid of him by sending him to the underworld, but instead, he ends up ruling it due to his natural leadership skills and the respect he gains from the underworld creatures.
One idea could be that Amelia is a new arrival in the Naruto universe's underworld. Maybe she has some unique powers that draw the attention of the various criminal elements, including some of Naruto's foes. Naruto, being the hero, gets involved to protect her and discovers there's more to her than meets the eye.
In this fanfiction, Naruto might leave the underworld because he has a mission to fulfill in the real world. Maybe he has to stop a new threat that endangers both the living and the underworld.
There could also be original characters created specifically for the fanfiction. These characters could be hybrids of the Naruto and Selene universes, perhaps having a mix of ninja abilities and Underworld powers. They could add new dimensions to the story and help drive the plot forward, whether as friends or foes to Naruto and Selene.
Sasuke could also be a main character in this fanfiction. He might be interested in the power of the lycans, seeing it as a way to gain more strength for his own goals. His brooding nature and his search for power could lead him into the lycan underworld, where he has to make choices about whether to ally with the lycans or use them for his own purposes.