Perhaps it's a water - based sea serpent. Since Naruto has some connection to the toad summons already, having a water - based summon would add a new dimension to his abilities. The sea serpent could be used to control water bodies, create tsunamis in battles near the coast, or even travel underwater at great speeds.
It could be a giant eagle - like creature. Eagles are often associated with freedom and power in many mythologies. Naruto could summon it to gain an aerial advantage in battles, allowing him to quickly move across the battlefield or scout areas from above.
One possible plot could be that Naruto discovers an ancient and forgotten summoning contract. Maybe it's for a powerful and mysterious creature that no one has summoned in ages. He then has to figure out how to use it, facing challenges like deciphering the contract's unique requirements. For example, it might require a special type of chakra that Naruto has to develop. As he works on this, he could face opposition from other villages who fear the power this new summoning could bring.
Well, he might gain access to super powerful summons that no one has ever seen before. These could give him an edge in battles, like against the Akatsuki.
It could be a young, inexperienced ninja who accidentally summons Naruto while trying to perform a different summoning jutsu. Maybe they were aiming for a small animal to help them with a simple task, but due to their lack of skill, they end up with Naruto. Another possibility is an enemy of Konoha who wants to use Naruto as a bargaining chip against the village. They think that by having Naruto in their hands, they can force Konoha to meet their demands.
It could be a new, young ninja who stumbles upon the cobra summoning contract by accident. This would be an interesting take as they start from scratch learning about the cobras and their powers.
Perhaps they are ancient water spirits. These spirits could have the power to manipulate water in ways that normal ninjutsu can't. They could turn water into solid ice sculptures that can be used as shields or weapons. They might also be able to swim through the ground as if it was water, allowing Naruto to surprise his enemies from below.
It could be someone who is jealous of Naruto getting the monkey contract. Maybe a rogue ninja who wants the power for himself.
He might be really confused at first. Naruto is from a world of ninjas and chakra, while the Potterverse has magic wands and spells. He could try to use his ninja skills there and end up causing chaos as people don't understand what he's doing.
He would become more confident. Having a rare summoning contract would be a big deal, and it would boost his self - esteem.
A character like Rock Lee could be an interesting choice for the main character in a 'Naruto Girls Summoning Contract Fanfic'. He is known for his hard work and determination. With this summoning contract, he could use the skills of the summoned girls to complement his own taijutsu - based fighting style. Also, his positive and energetic personality would make for an interesting dynamic with the female characters he summons.
Well, he might first try to figure out which animals are associated with the contract. If it's a contract for a powerful and rare creature like a phoenix, it could lead to him having a unique and extremely powerful summon. Maybe he'll face some challenges in understanding the terms of the contract, like some kind of ancient language or special requirements.