One idea could be a human summon from a long - lost clan with unique powers. For example, a summon from a clan that can control time in small increments. This human summon could be an ally to Naruto in a difficult battle against a new, powerful enemy.
Another plot idea is a human summon who is a diplomat from a far - off land. This human summon comes to the Hidden Leaf to form an alliance, but there are enemies within the village who don't want this to happen. Naruto has to protect the human summon while also trying to figure out who is behind the opposition to the alliance.
Maybe a human summon who is a master of ancient ninja arts that have been forgotten. This character could teach Naruto and his friends these arts, adding a new dimension to their fighting abilities. They could use these arts to defend the Hidden Leaf from a threat that normal ninjutsu can't handle.
Maybe the chameleon is from a long - lost clan of summon animals that were thought to be extinct. And it holds the key to a powerful jutsu that was lost in time. Naruto discovers this when he first summons the chameleon and has to go on a journey to unlock the jutsu's potential.
One idea could be a story where Naruto discovers a new type of frog summon that has a unique ability, like the power to control water in a way no other frog can. This could lead to him facing new challenges and enemies. Another plot could involve Naruto's frog summons going on a mission without him, and he has to find a way to communicate and guide them from afar. Maybe they encounter a powerful enemy in the frog realm that they need Naruto's help to defeat.
One idea could be that Naruto discovers a hidden dragon summoning scroll. He tries to master the summoning technique, but the dragons are very powerful and difficult to control at first. Another plot could involve a dragon that has a special connection to Naruto's family history. Maybe his mother or father had a pact with the dragons long ago.
Perhaps the Knights of the Round are summoned by accident when Naruto is trying out a new experimental jutsu. They initially misunderstand their purpose in this new world and cause some chaos. But as they learn about Naruto's world and his cause, they decide to help him in his fight against the Akatsuki. They could offer strategic advice based on their own experiences in their home realm.
Perhaps the bat summon is from a cursed place, and when summoned, it brings a dark influence. The Naruto characters then have to find a way to break the curse on the bat and its place of origin. This could involve a journey to discover the history of the bat summon and the secrets of the place it comes from. It would be a story full of mystery and danger.
One idea could be that Naruto summons a special fox with unique powers that helps him defeat a powerful enemy in a new and unexpected way. For example, the fox might have the ability to create illusions so strong that they can mislead even the most powerful ninjas. Another plot could involve Naruto using the summoned foxes to explore a hidden part of the ninja world that was previously inaccessible. Maybe the foxes know the secrets of an ancient ruin and lead Naruto there, where he discovers new jutsus or artifacts.
One idea could be a pony being summoned in the Naruto world and having to adapt to the ninja way. For example, it might use its unique pony abilities like magic or flight in combat, which would surprise the Naruto characters.
One idea could be a story where a character creates a human puppet of a long - lost ninja. This puppet could hold the memories of the original person and be used to uncover secrets from the past. For example, it might remember a hidden jutsu or a secret alliance that was long forgotten.
Perhaps in the fanfiction, the leviathan is a sentient being from a different dimension. Naruto forms a bond with it not just as a summon but as a friend. They communicate telepathically, and the leviathan helps Naruto understand some of the deeper secrets of chakra by showing him how it manipulates energy in its own dimension.
Maybe the Cerberus in the fanfiction has a special connection to the Nine - Tailed Fox. It could be that they are both from an ancient and powerful lineage. The Cerberus could be a guardian of some sort, and its summoning requires the main character to prove their worthiness, perhaps by passing a series of trials in a mysterious realm.