Obviously Naruto could be one of the main characters. He would bring his unique abilities and his never - give - up attitude. Another could be Rick from The Walking Dead. His leadership skills combined with Naruto's power would make for an interesting dynamic. They could learn from each other and lead the survivors in different ways.
One possibility is that Naruto and Michonne could be main characters. Michonne is a badass with her katana skills and Naruto's ninjutsu would complement that. Naruto could also befriend Daryl. Daryl's survival skills in the wild and Naruto's combat skills could create some really cool scenes. And perhaps Kakashi from Naruto could also be a main character, guiding the survivors with his wisdom and his Sharingan - related abilities.
There could be a new type of hybrid creature that is a result of the combination of the zombie virus and some supernatural element from Bella's world. This hybrid could be extremely powerful and unpredictable, and it sees both humans and zombies as a source of food or something to dominate, making it a very dangerous antagonist in the fanfiction.
Obviously Naruto would be one of the main characters. Depending on the plot, Sasuke could also be involved, either as a helper or an obstacle. Sakura might also play a role, perhaps as a healer trying to save Naruto. There could also be new characters created specifically for this fanfiction, like a dark figure who is responsible for Naruto's 'dead man walking' situation.
One possible plot could be that Naruto and his friends somehow end up in the world of The Walking Dead. Naruto's ninja skills would be really useful in fighting off the zombies. He could use his shadow clone jutsu to create distractions while they look for supplies or a safe place. His friends like Sakura could use her medical skills to treat any survivors they come across. And Sasuke could use his sharingan to detect any hidden threats, either from the zombies or from other groups of survivors.
Kakashi could be another important character. As a mentor figure, he might be guiding the younger generation through the difficult times after Naruto's death, using his experience and wisdom to keep the village stable.
One possible plot could be that the zombies from The Walking Dead somehow end up in the Naruto world. Naruto and his friends have to use their ninja skills to fight off the hordes of zombies. Maybe they could also try to find a cure using their knowledge of chakra and medical ninjutsu.
She could interact with Rick. Rick is the leader of the group in The Walking Dead, and he would be very interested in Zoey if she has any skills or knowledge that could help the group survive. Maybe she has some medical knowledge, and Rick would want her to take care of the injured in the group.
Sasuke could also be a main character in such fanfiction. Given his complex past and his own journey of redemption, he might be able to relate to a 'dead man walking' character. He could either be a rival or an ally to this character, depending on the plot of the fanfiction.
Lee Everett is often popular. His moral compass and leadership in the original game make him an interesting character in crossovers. He can bring his survival skills and decision - making abilities to new situations in the crossover fanfiction.
Definitely Naruto himself. He's the main character of the Naruto series, so he has to be there. In a crossover with Attack on Titan, he could meet Eren. Naruto's determination and Eren's drive to protect his people could make for an interesting dynamic between them.
Obviously, Naruto would be one of the main characters. His determination and never - give - up attitude would be very useful in a zombie - filled high school. Sakura could also be a main character, using her medical ninjutsu to try and find a cure for the zombie virus. And Sasuke, with his powerful combat skills, would be great for fighting off the zombies.