In the fanfiction world, there could be all sorts of magical or special circumstances. Maybe the baby girl has some special power that only Naruto can sense. So, he keeps her close to figure out what that power is and how it can be used for good, or to protect her from those who might want to use her power for evil.
He could decide to protect the baby girl himself. Naruto has a big heart. He might see the baby as someone he needs to look after, just like how he was always looking out for his friends. Maybe he starts teaching her some basic ninja skills when she grows a bit older.
The baby could turn out to have some sort of special chakra. Naruto, being curious and always wanting to help, tries to find out more about it. He might seek help from Kakashi or other experienced ninjas.
Perhaps Hinata will be really confused at first. She could ask her friends for help, like Naruto. Together, they would try to figure out where the baby came from and what to do with it. Since Hinata is kind - hearted, she'll surely do her best to keep the baby safe and comfortable.
In terms of the story's development, it could lead to a whole new arc. Naruto's transformation into a baby girl could be a sign of a greater threat to the ninja world. It might be related to some ancient curse or a new enemy's plot. And as he tries to figure out how to turn back, he would have to rely on his friends and his own inner strength in a different way than before.
Well, she could try to find a way to return him to his normal form. Maybe she'll search for some ancient magic or consult with a powerful sorcerer in the feudal era.
Naruto could find a book that tells the story of a great hero who was just like him, full of energy and a desire to protect. This could inspire him to new heights. He might also accidentally trigger a trap or a hidden mechanism in the library while exploring, leading to an adventure filled with challenges and puzzles to solve.
Well, he might put on the suit and suddenly feel a new sense of confidence. Maybe he uses it to infiltrate an enemy hideout. He could pretend to be a rich merchant or something, and use his ninja skills along with this new disguise to gather intel.
It's possible that the tomb contains the remains of a powerful shinobi from the past. Naruto could learn about their history and the secrets of their power. For example, if it was an Uzumaki ancestor, he might find out more about his own clan's abilities. This could lead to him unlocking new forms of his chakra or even new ways to use the Nine - Tails' power.
Well, he could use the armor to enhance his combat abilities. Maybe it has some special powers like increased speed or strength. He might also discover a connection between the armor and an ancient ninja clan, which could lead to new adventures and unlocking more of his potential.
In such a fanfiction, Naruto might take the child under his wing. He could start teaching the child some basic ninja skills, like how to throw a kunai properly. Maybe he'd also share his own experiences of growing up as an outcast in the village, inspiring the child to be strong.
He could also find that the scroll has a connection to his family. It might hold secrets about his parents or his Uzumaki heritage. This could lead him on a new quest to learn more about his roots and the powers that might be associated with his family. It would be an interesting plot twist.