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.
The story could be about Naruto creating a new and unique summoning contract. Maybe he discovers a new type of creature that no one has ever summoned before. He could form a bond with these creatures, and they could have special abilities that help him in his battles or quests. For example, they might be able to control a certain element in a new way or have stealth abilities that Naruto can use to his advantage.
A likely main summon could be Gamabunta. He's big, powerful, and has a long - standing relationship with Naruto. He could teach Naruto some really advanced water - based jutsu.
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.
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, Tsunade could be a great helper. She has extensive knowledge of chakra control and medical ninjutsu. She could teach Naruto how to use his chakra more precisely when creating the Rasengan, perhaps by showing him some medical - ninjutsu - based chakra control techniques that can be applied. Minato, Naruto's father, could also play a role. He was the one who originally created the Rasengan. He could appear in Naruto's dreams or in some sort of time - travel scenario and show Naruto some hidden aspects of the Rasengan creation that he didn't know before. And then there's Sakura. She's become very strong over time. She could use her strength and knowledge to assist Naruto, maybe by creating some sort of training regimen for him to improve his Rasengan creation skills.
He might gain enhanced speed and strength. The fox is known for its agility and power, so when summoned, it could transfer some of those traits to Naruto. For example, he could run faster than he already can and deliver more powerful punches.
If the summoning contract has a connection to a particular family in the village, it could improve Naruto's standing with that family. He might be invited to their family events and be seen as an honorary member. However, if the contract is related to a dark or secretive part of the village's past, some villagers might be afraid of Naruto and try to distance themselves from him.
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.