In this fanfiction scenario, Hiccup's personality would be a mix of his old self and new vampire traits. He'd still be the intelligent and creative Hiccup we know. But his confidence could grow in a different way. Instead of relying on his inventions and dragon - training skills, he'd start to rely on his vampire powers. This could make him a bit more cocky at times. At the same time, he'd be more in tune with the night and solitude, which could make him seem more mysterious to those around him. His relationship with Toothless would also be affected. He might worry that Toothless won't accept him now that he's a vampire, but in reality, Toothless would probably still be his loyal friend.
His confidence might increase even more. Naruto was always confident as a ninja, but as a sorcerer, he has new powers at his disposal. He would feel even more capable of taking on challenges. For example, if he faces a powerful sorcerer enemy, instead of being intimidated, he would be eager to test his new abilities.
He might become more patient. As a medic, he has to be careful and take his time with patients, which is different from his impulsive fighting style.
Naruto's usually impulsive personality might become more calculating as a puppet master. He would need to think ahead when using puppets in battle, so he'd be less likely to rush into things.
In the 'Fire Emblem Robin Becomes a Dragon' fanfiction, his personality change could be complex. At first, he may be confused by the new emotions and instincts that come with being a dragon. This could make him seem moody or unpredictable to those around him. But as he gets used to his new form, he might develop a more confident and assertive side. His sense of justice, which was present in his human form, could be magnified. He might be more likely to take on powerful enemies without hesitation, seeing it as his duty as a powerful dragon. And yet, he may also have moments of vulnerability when he misses his human form and the relationships he had in that state, which could add depth to his character in the fanfiction.
Naruto's personality might become more reserved in some ways. As Hokage, he has to represent the village in a more solemn and diplomatic manner. He can't be as carefree as he used to be. For example, in international meetings, he has to think carefully about his words and actions.
At first, Elena might be shocked and a bit scared when she finds out. Their relationship could become strained as she has to adjust to the idea of her brother being a vampire. But over time, they could grow closer as Jeremy learns to control his vampire side and Elena sees that he's still the same person deep down.
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 personality might become more cautious. Since he has a greater responsibility as a guardian, he can't be as reckless as he was sometimes in the original Naruto series.
His personality might become more withdrawn. As a lich, Naruto could be feared by others, and this might make him more hesitant to interact with people. He was always so outgoing before, but now he might keep to himself more.
Naruto may also become more solitary. Sparda often fought alone, and Naruto, influenced by this, might start to distance himself from his friends at first. However, he would still have that underlying loyalty and would eventually find a way to balance his new - found independence with his relationships.