Jiraiya could be a great addition. Since he was Pain's teacher, his presence could add a lot of depth to the story. He could offer insights into Pain's past and also help Naruto understand Pain better.
Konan could be really interesting. In some fanfictions, she might have a different backstory or motivation that affects the Naruto vs Pain fight. For example, she could be secretly trying to stop Pain from going too far in his destruction of the Leaf Village.
I think Hinata would be an interesting character to include. She has her own unrequited love for Naruto. Her presence could add some drama to the story as she sees Naruto getting closer to Ahri. Another good character could be Jiraiya. His lecherous yet knowledgeable self could provide some comical relief and also give some sage advice to Naruto and Ahri when they need it.
Sasuke from Naruto could be a great addition. His brooding nature and powerful ninja skills would contrast well with Musubi's more upbeat and energetic personality. Also, Konohamaru could be included. He looks up to Naruto and his presence could add some humor to the story as he tries to impress Naruto and Musubi.
Hinata could be included. Her gentle nature could have a positive impact on Inari, and she might be able to teach him some of her own ninja techniques. Shikamaru could also be part of it. His intelligence would be valuable in planning strategies, whether it's for defending the Land of Waves or dealing with other threats. Also, Tsunade, as she could offer her leadership and medical expertise if needed.
Sakura could be a great addition. She could be Hinata's best friend and give her advice on her relationship with Naruto. She might also be a bit jealous at first but then come to fully support them.
Kakashi would be a great addition. His wisdom and combat skills could add depth to the story. He could act as a mentor figure, guiding Naruto and Sasuke through the strange situations they find themselves in due to the fox - related elements.
Obviously, Naruto and fem Pain are the main characters. Naruto, with his strong will and determination to protect his friends and the village. And fem Pain, who might have a different take on the Akatsuki's goals compared to the original Pain in the Naruto series.
One great 'Naruto x Pain Yaoi Fanfiction' is 'The Bond Beyond Battles'. It delves deep into the complex relationship between Naruto and Pain. It shows how their opposing views could gradually turn into a unique understanding and an unexpected bond. The story is well - written, with great character development and it keeps you hooked from start to finish.
I would recommend 'Pain's New Beginning'. In this fanfiction, Pain gets a chance to relive his life after a strange encounter. It has some really cool plot twists that keep you hooked. It also explores his relationships with other characters in new ways.
Sakura could be a great addition. She could provide medical support during their adventures or offer her combat skills when needed. Kakashi would also be a good choice. His wisdom and experience could guide Naruto and Princess Yuki in difficult situations.