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.
With his human friends, there could be a period of estrangement. Some might fear him, while others might be overly curious. Hiccup would have to work hard to regain their trust. His relationship with Toothless could also evolve. They might share a deeper bond as they both have a connection to two different worlds. Toothless could help Hiccup understand his dragon half better, and Hiccup could use his human knowledge to protect Toothless in new ways.
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.
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.
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 Toothless would be very different. Toothless might be initially confused and a bit hesitant around Hiccup in his new form. But as time passes, they would develop a new kind of bond based on Hiccup having to adapt to being a dragon. With Astrid, it could be strange at first. Astrid might be both curious and a bit jealous of Hiccup's new dragon form. She would have to see Hiccup in a whole new light.
They might develop their relationship through shared experiences. For example, if they both get lost in an uncharted area, they have to rely on each other to survive. The half - dragon could use its natural instincts to find food and shelter, while Hiccup uses his intelligence to figure out how to get back home. This mutual dependence would strengthen their bond. Also, they could communicate through body language and simple sounds at first, gradually developing a deeper understanding of each other as time passes.
His relationship with Astrid would become really strained. She'd be heartbroken that he doesn't remember their relationship, and she'd have to work hard to make him fall in love with her all over again. It would be a journey full of mixed emotions for her, from sadness to determination.
His relationship with Toothless would change drastically. Instead of being the rider, he becomes like a little sibling or a young apprentice to Toothless. Toothless would have to be more protective and patient with Hiccup.
His relationship with Toothless would be very different. Toothless might be more protective of him in his new form, as if sensing that Hiccup is more vulnerable as a female Night Fury. And Hiccup would have to communicate with Toothless in new ways, perhaps using more body language that is typical of female Night Furies.
Hiccup could have wings that are small and not fully developed at first. They could be hidden under his clothes most of the time. His skin might have a sheen to it, like the shiny scales of a dragon. His ears could be slightly pointed, and he might have a tail that he tries to keep hidden from the humans. His overall appearance would be a strange and unique blend of human and dragon features, making him both fascinating and a bit intimidating to those who see him.
Hiccup's friends would be extremely worried. Astrid, being Hiccup's closest friend and love interest, would probably be the first to take action. She would gather the other riders and start planning a rescue mission right away. Snotlout might initially be a bit hesitant, but the thought of losing Hiccup would push him to join in. Fishlegs would use his knowledge of dragons to figure out where Drago might be hiding Hiccup.