Hiccup's relationship with his father (if his father is still alive in the fanfiction) would be complex. His father might be proud of him for achieving such a powerful status, but also worried about how the other tribes would react. Hiccup would also have a different relationship with the dragons in general. He would no longer be just a friend to them, but a leader, a dragon god. This could lead to some dragons being more submissive to him, while others might test his new authority.
His relationship with Astrid might become more complicated. She might be initially shocked or even a bit scared of his half - dragon side. But as she gets to know that it doesn't change who Hiccup really is, they could grow closer. His dragon friends, on the other hand, might see him as more of an equal now that he has a dragon part in him.
His relationship with Mary Jane would likely change a great deal. She might be in awe of him, but also a bit intimidated. Peter, now a god, would have to struggle to maintain the same level of intimacy they once had. With his friends like Ned, they might see him more as a protector. Ned would probably be excited about Peter's new powers at first, but then realize that their friendship has become more complex. And his enemies? They would either be terrified of him or try to find a way to bring him down.
His relationship with Annabeth would likely be very different. Annabeth, who is used to Percy as a hero in a more traditional sense, might struggle with his new, more war - like persona. There could be tension as she tries to understand the new Percy. She may worry that he's becoming too violent or cold - hearted.
His relationship with Sasuke would be very different. Sasuke might view Naruto with a new sense of awe and respect. Instead of their rivalry, Sasuke could become Naruto's most loyal follower or partner in maintaining the balance of the new world Naruto as a primordial god would oversee. With his friends like Sakura and Kakashi, Naruto would be more of a protector. They would look up to him not just as a friend but as a divine being.
His relationship with Sasuke would be very interesting. Sasuke might be initially suspicious of Naruto's new form, but eventually, they could bond over Naruto's struggle to control his powers and use them for good. It could be a new level of rivalry and friendship.
With his human friends, it would be really tough. They might be scared of him at first. Astrid, for example, would be conflicted. She was attracted to Hiccup as a human, but now he's a dragon. She would have to overcome her fear and try to find a way to communicate with him. And Hiccup would feel isolated from his human friends, longing for the connection they once had.
His friends might be initially scared. But then, they would likely be determined to help him. For example, Lucy might use her celestial magic to find a way to reverse the transformation. Their relationship would become more of a caretaker - patient one in the short term.
His relationship with Lucy would become more complex. She might be in awe of his new power but also worried about losing the Natsu she knew. His friendships in the guild could also be strained as they might see him as a different person now. Some might be jealous of his new status, while others would be afraid that he'll leave them behind.
It can strengthen his bond with Toothless even more. Since they already have a deep connection, the dragon blood could make them almost telepathic. They would understand each other without even having to speak or make gestures.
His relationship with Sasuke would be really interesting. Since Sasuke has his own complex connection to the Uchiha clan and Madara, Naruto becoming a Madara fan could either bring them closer together in understanding the Uchiha's past or drive them further apart if Sasuke doesn't agree with Naruto's new - found admiration. Maybe Naruto would start to push Sasuke towards a more 'Madara - like' view of power and revenge.