Romantically, it could be quite a challenge. If he was in a relationship before the name change, his partner would need to get used to the new name. And if he was looking for a new relationship, he'd have to introduce himself differently. It might attract different types of people who are interested in the mystery of his new identity rather than the 'Harry Potter' they thought they knew.
With his friends, it could initially cause confusion. They are so used to calling him Harry that the new name might be a bit of a shock. But if they understand his reasons, they would likely support him. For example, Hermione might be the first to adapt and help others adjust, using her logical thinking to see the benefits of the name change.
His relationship with the wizarding world at large would be greatly affected. People have put so much hope and expectation in 'Harry Potter'. With a new name, he could either be overlooked or seen as an impostor. Some might think he's trying to escape his responsibilities, while others might see it as a fresh start for him and be more accepting.
If Harry changes his look to seem more intimidating, it might make some of his enemies more cautious around him. For example, if he has a more severe look with a long beard and a scowl, the Death Eaters might think twice before attacking him. As for his friends, they might be a bit taken aback at first but would quickly accept the new look.
It might make his friends a bit wary at first. Since this is an unusual and powerful thing to happen, they could be concerned about how it's changing Harry. But as they see that Harry is still the same person deep down, they would gradually accept it.
If Harry absorbs the memories of his enemies, it could make his relationships with other characters more complicated. For instance, if he absorbs the memories of Draco Malfoy, he might understand Draco's family pressures better. This could lead to a more complex relationship where Harry has both sympathy and still some animosity towards Draco.
His relationship with Ginny might be affected. Ginny could be very protective of him and worry a great deal. This could lead to some sweet, tender moments between them as she takes care of him during his seizures.
In this fanfiction scenario, Harry's relationship with Dumbledore could be very interesting. Dumbledore would surely be aware of the significance of Excalibur. He might take Harry under his wing even more, guiding him on how to use the sword's power for good. Harry's relationship with the other Hogwarts students could also change. Some might look up to him even more, while others might fear him because of the great power he now wields.
If Harry is sleepwalking, it might worry his friends. For example, Hermione would probably be very concerned and try to find a way to stop it. This could strengthen their friendship as she devotes time to helping him. Ron, on the other hand, might initially find it funny but then also realize the seriousness. It could also make some of his classmates more curious about him, which could either bring them closer or create some distance depending on how they react to his sleepwalking episodes.
His intelligence might make him more respected by his peers. Instead of just being known for his scar and his connection to Voldemort, his friends see him as a true intellectual. Hermione might become more of an equal to him in terms of academic discussions rather than just being the one who always has the answers. Ron, on the other hand, could feel a bit intimidated at first but then grow to be proud of his friend's intelligence.
His friends might be initially terrified. Hermione, for example, would be both scared and immediately start researching how to reverse it. Ron would probably be more shocked and not know how to react at first. Their friendship would be tested as they try to figure out what to do. They might have to keep Harry's transformation a secret from other students to protect him from being hunted or experimented on.
The transformation would have a huge impact. Harry's friends would have to re - evaluate their relationships. Some might be more protective, like Neville. Others might be a bit distant because they don't know how to act around a girl - Harry. And Harry himself would have to navigate new social dynamics, which could be both challenging and interesting.
His relationships with his teachers could also change. Dumbledore might look at Harry with more sympathy and offer him different kinds of guidance. Snape, although still prickly, might secretly respect Harry more for enduring this new hardship, or he could use it as an excuse to be even more critical, thinking that Harry is now more likely to make mistakes.