One possible plot could be that Harry discovers he has some long - lost connection to the Malfoy family. Maybe he finds out through some ancient magic or a hidden family secret. This could lead to him having to re - evaluate his entire view of the Malfoys, especially Draco. He might start to understand Draco's actions in a different light and even feel a sense of kinship with him.
Hermione would probably be very skeptical at first. She would want to research every aspect of this new discovery. Ron would be more likely to be angry or at least very confused. He has always seen the Malfoys as the enemy, so the idea of Harry being one of them would be hard to swallow. Draco, on the other hand, would be quite smug. He might think that Harry is finally realizing that the Malfoys are superior in some way.
One of the most interesting aspects in this type of fanfiction is seeing Harry's initial shock. He has grown up in a non - magical world, so suddenly realizing he's a wizard would be overwhelming. He might first doubt it, thinking it's some kind of joke or mistake. But as the story unfolds, he starts to see the evidence around him, like strange things happening that can't be explained by Muggle means.
His relationship with Hermione and Ron would be different. They might be a bit jealous at first of his new powers. But they would also be curious and try to help him understand his demigod side.
In this fanfiction, Harry could be thrown into a whole new world of Greek mythology. He might have to go on quests, just like the traditional demigods. His friends at Hogwarts would be really confused when he starts showing these new demigod - like abilities. And he'd have to learn about his new heritage, which would be a huge shock considering he thought he was just a wizard.
In the fanfic 'Malfoy's Revelation', Malfoy is paired with Harry for a project. As they spend time together, Malfoy notices some strange behaviors from Harry, like flinching at sudden movements. After some snooping around, he discovers that Harry has been abused. This new knowledge makes Malfoy more empathetic towards Harry and he tries to help him in his own way, which includes standing up for Harry against some of their mutual enemies at Hogwarts.
In this fan fiction, Harry might initially deny the whole thing. But as he starts to explore this new side of himself, he could discover some hidden secrets about the Malfoy family. This could change his perception of the Malfoys completely. And who knows, it might even lead to a new form of magic or power that he has access to because of his newfound 'Malfoy - ness'.
Hermione would probably be involved. She's always by Harry's side when it comes to solving mysteries. She could use her vast knowledge to help Harry figure out what's so special about Vault 99. Ron might also be there. He's Harry's loyal friend and would be ready to back him up in any adventure related to Malfoy and the vault.
The plot could center around the mystery of Vault 99. When Harry finds out Malfoy has access to it, he starts investigating. He might discover that the vault holds some sort of power or knowledge that could change the wizarding world. Harry would then be in a battle of wits with Malfoy to either gain control of the vault's contents or prevent Malfoy from misusing them. This could involve sneaking around Hogwarts, using magic to uncover clues, and facing off against Malfoy's allies.
Well, Harry Potter is the main character as the story revolves around his discovery. Draco Malfoy is crucial as it's a 'Malfoy Romance' story. There could also be new characters introduced that are related to the Malfoy family's secrets. Ginny Weasley might also be in the picture, perhaps being jealous or trying to understand Harry's new connection. And don't forget about Dumbledore, who might have known something all along and could offer some guidance to Harry in this strange new situation.