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.
Some fanfictions could explore the idea of Selene teaching Naruto about the secrets of the Underworld. Naruto, in turn, could show Selene his ninja way and how determination and hard work can overcome great obstacles. This could lead to a series of adventures as they explore different regions of the Underworld together.
Well, Naruto's Nine - Tails chakra is a huge power source. If he were to share some of that chakra with Selene, she could gain new abilities. Maybe she could use it to create a powerful shield around them, since the Nine - Tails' chakra is known for its raw power. On the other hand, Selene's power to control the blood of her enemies could be used to immobilize opponents while Naruto prepares his more complex jutsus. Their combined powers would be a very interesting and powerful mix that could be used to overcome many difficult challenges in the Underworld.
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.
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.
One possible plotline could be that Naruto, with his strong will and unique powers, somehow finds himself in the Underworld and meets Selene. They might initially be at odds as they come from very different worlds. Naruto could be intrigued by Selene's vampiric nature and her power over the night. They could form an unlikely alliance to face a common threat in the Underworld, like a powerful dark force that is threatening to disrupt the balance not only in the Underworld but also has implications for Naruto's own world.
Since we don't have much information about 'Selene Love Story', it's difficult to say exactly who the main characters are. But surely Selene is one of them. There might be a male lead, perhaps someone who is Selene's love interest. It could also have supporting characters like Selene's friends or family members who play important roles in the story, for example, by either supporting or opposing her relationship.
The main characters are Harry, who is used to being in the wizarding world of Hogwarts, and Selene. Selene is probably a powerful character with her own set of abilities. In the fanfic, their interactions will be the focus, as Harry adjusts to being adopted by her and they form a new kind of relationship.
One possible fanfiction could be that Selene and Michael's pregnancy is a sign of hope for the vampire and lycan clans. Their child could be seen as a symbol of unity, bringing an end to the long - standing feud. Maybe in the story, they have to face many challenges during the pregnancy, like threats from those who oppose the union of a vampire and a lycan.
A common theme is the relationship between Selene and the OC. It could be a friendship, a mentorship, or even a romantic relationship. For example, the OC might be a new vampire that Selene takes under her wing.
First, you need to understand the Underworld universe. Know the rules about vampires, werewolves, and the whole power dynamic. For the OC, create a unique backstory. Maybe they're a human with a special connection to the supernatural world. Then, think about how Selene would react to this new character. Their first meeting should be impactful and set the tone for their relationship.