Who might visit Harry while he lives alone at Grimmauld Place in the fanfic?

Well, the plot could involve Harry exploring the secrets of Grimmauld Place on his own. Maybe he discovers hidden rooms filled with old Black family magic items. He might also struggle with feelings of loneliness and isolation, but at the same time, use the solitude to practice his magic without distractions.

His old mentor, Iruka, might visit. Iruka has always cared about Naruto. He could bring some supplies and words of encouragement. He might also be worried about Naruto's well - being and want to make sure he's okay living in the cave.

He will most likely meet Sirius Black. Sirius is an important figure in Harry's life and his presence at Grimmauld Place is quite significant. They could have a deep conversation about Harry's anger and what to do next.

Maybe some of the younger ninja like Boruto or Sarada could stumble upon Naruto's cave while on a training mission. They could be curious about this strange hermit - like figure in the cave and later realize it's Naruto. This could lead to a mentoring - like relationship between Naruto and the new generation.

His best friends, Ron and Hermione, would most likely visit him. They have always been by his side through thick and thin, so they would find a way to get to the tent to check on him, bring him supplies, and offer their support.

It could be that there is no traditional 'antagonist' in the sense. Maybe it's just the situation and the conflict between Harry and Ron's personalities. But if we had to consider one, it could be an outside force that is influencing Ron's actions and making Harry distrust him. For example, a new dark magic object that is affecting Ron's judgment.

He might meet a mysterious old wizard who has been traveling the seas for centuries, gathering knowledge of different magics. This wizard could be a great source of wisdom for Harry.

His best friends Hermione and Ron would surely visit. They might come to help Harry set up new magical experiments or just to relax away from the hustle and bustle of the wizarding world.

Arthur could visit Merlin in the tower. He might be curious about what Merlin does in his secret place or he could be in need of Merlin's help and follows him there.

Hermione might visit Harry. She would probably be worried about him living alone and bring him some books she thought he'd like or some new potions she'd been working on.