Sasuke would be extremely angry and determined to rescue Naruto. He would immediately start formulating a plan, using all of his skills and knowledge. He might even consider making some dangerous bargains or alliances if it means getting Naruto back.
The Leaf Village would be in chaos at first. Hinata is an important member of the Hyuga clan, and her kidnapping would not be taken lightly. The Hokage would immediately call for an emergency meeting. They would start by sending out search teams, likely led by some of their best shinobi like Kakashi or Shikamaru, who are known for their intelligence and combat skills.
Sakura would probably be shocked at first, but then she'd get angry. She'd immediately start to struggle and try to free herself. She might call out for help if she thinks there are allies nearby.
The other Konoha ninjas would be quite shocked. The Hokage, whoever it is at that time, would see Naruto's change as a potential threat to the village's stability. They would likely keep a close eye on him and try to figure out what caused this transformation. Meanwhile, the younger generation of ninjas who looked up to Naruto would be confused and disappointed. They expected Naruto to be their role model of a kind - hearted and positive ninja, not someone acting like the feared Madara.
Yes, there are likely some fanfictions with this concept. Fanfiction writers often come up with unique and creative ideas, and the idea of Naruto having some sort of special connection or relationship with Kaguya Otsutsuki in a fan - created story is not unheard of. It could involve Naruto exploring Kaguya's past, or perhaps having a role in her redemption in the fanfic's alternate universe.
Sasuke might be a bit taken aback at first. He's used to Naruto's normal look, and this change could make Sasuke see Naruto in a new light, perhaps as a more formidable opponent or an even stranger ally. Sakura would probably be shocked too. She might tease Naruto about it at first but then grow to accept it. Kakashi would likely raise an eyebrow and make a comment about how Naruto is always full of surprises with his new look.
The theme of mystery is also common in Kaguya Otsutsuki fanfiction. Her character has a lot of mystery surrounding her, and fanfictions often try to solve these mysteries. For example, what was her life like before she came to the ninja world? And what secrets does she still hold? Writers use these questions to create engaging stories.
A common theme is power discovery. Sakura often discovers new powers related to the Otsutsuki in these fanfictions. For example, she might unlock some unique abilities that are connected to their ancient lore.
One possible plot could be that Naruto discovers he has some hidden Otsutsuki bloodline. This leads to him being ostracized by some in the village who fear his new - found power. He then has to go on a journey to learn about his Otsutsuki heritage, facing challenges along the way and also having to prove that he's still the same Naruto at heart.