Yes, it might be dangerous. In the 'girl licked by dog story', depending on the dog's health status. If the dog has rabies or other contagious diseases, there is a high risk. Even if the dog seems healthy, there could still be bacteria in its saliva that can cause skin infections or other health problems for the girl, especially if she has a weakened immune system.
Perhaps it was a weapon created by a rogue ninja with unique powers. And for some reason, it found its way to Naruto in Wave. It might also be a weapon that was enchanted by a sorcerer long ago and has special abilities that Naruto will discover as he uses it.
In the 'girl licked by dog story', if a girl is licked by a dog, she has to take it seriously. Firstly, make sure the dog is vaccinated. If it is, that's a bit of relief. However, she still should clean the area gently. If she has any open wounds on her skin where the dog licked, she must go to a hospital without delay. The medical staff will run tests if they think it's necessary. For example, they might test for certain bacteria or parasites that could be transmitted through the dog's saliva. She also should inform her parents or guardians about this incident right away.
I don't think it's true. 'The Licked Hand' is more likely a fabricated tale. Maybe it incorporates some common themes or tropes but doesn't stem from actual happenings.
On the positive side, new and better policies could be implemented. If the old council was corrupt or stagnant, getting rid of them would open the door for fresh ideas and reforms. Naruto could bring in new people with different perspectives to help run the village, leading to a more prosperous and fair Konoha.
His teammates, Sasuke and Sakura, would surely be involved. Sasuke, although he may not show it as much, still cares about Naruto. He would keep an eye on Naruto's condition, and if there was any sign of danger, he would be ready to protect him. Sakura would be more hands - on with the medical care, checking his temperature, giving him medicine, and making sure he rests properly.
One possible scenario in this fanfiction could be that Naruto's sister constantly interferes in his ninja training. She might think the training is too dangerous for him and tries to stop him from taking on challenging missions. For example, when Naruto is about to go on a mission to the Land of Waves, his sister could try to convince the Hokage not to send him, believing that he's not ready yet. This would add a whole new layer of conflict to the story, not just between Naruto and his sister, but also with the village's expectations of Naruto as a ninja.
A fanfiction about Naruto getting the Kusanagi could also involve a time - travel aspect. Naruto could be sent back in time and end up in the era when the Kusanagi was first created. There, he meets the original wielder and learns from them. He then brings the knowledge and the sword back to his own time, using it to defeat a great evil that was previously unbeatable.