One idea could be a story where Naruto meets Shelley Hennig in a mysterious new world. They have to team up to fight against an unknown evil force that threatens both their worlds. Naruto uses his ninja skills, and Shelley Hennig uses her wits and any special abilities she might be given in the fanfic.
Yes, Percy Shelley wrote fiction. His literary output was diverse, and fiction was part of it. However, his contributions to poetry are what he is most widely recognized for.
You can start by creating an interesting scenario where they meet. For example, Naruto could be on a mission in a strange land and suddenly come across Shelley Hennig. Describe the setting vividly, like the misty forest or a bustling city square where they first lay eyes on each other.