This incident could also introduce new storylines. Maybe Sirius tries to keep Harry and Draco apart, which then leads to a series of events where they have to find ways to be together or communicate secretly. Or perhaps Sirius' reaction causes other characters to get involved, expanding the scope of the fanfiction plot.
It could potentially strain the relationship. If Sirius misinterprets the situation, it might create some tension. Harry and Hermione would feel like they need to explain themselves, and Sirius might be a bit standoffish until he gets the real story. For instance, if he thought they were hiding something from him, it could make things a bit rocky between them for a while.
The plot could take a turn towards drama. Ron's reaction could create a rift between him and Harry, forcing Harry to choose between his old friend and this new - found connection with Draco. This would add a lot of tension to the story.
It could strengthen their relationship. If Harry handles it well, it shows his maturity and trust in them. They would likely appreciate that and become even closer to him.
If Lucius walks in, the power dynamic between Harry and Draco would likely shift. They would no longer be in their own little world and would have to deal with an adult authority figure. Draco might become more submissive to his father's commands, and Harry would have to face the wrath of Lucius, which could put him in a very difficult situation.
Sirius may also be angry at first. Given his protective nature towards Harry, if he misinterprets the situation as Draco causing trouble for Harry, he would likely step in assertively. But if it's a situation where Harry and Draco have a more positive or friendly interaction in the fanfiction, Sirius would have to re - evaluate his initial reaction.
Their talk could also enhance Harry's magical knowledge. Sirius could teach him spells or magical techniques that he hadn't learned at Hogwarts yet. This new knowledge would be very useful for Harry in his fight against the Dark Arts. Moreover, learning from Sirius would make Harry more independent in his magical growth as he gets advice from someone outside of the school environment.
The nighttime raving can also be a turning point in the plot. Say, Draco raves about his true feelings for Harry, like his admiration or his envy in a more complex way. This could change the direction of their relationship. They might start to see each other in a different light and form an unlikely alliance or a deeper friendship.
This event can greatly affect the plot. It can introduce a new conflict. For instance, the school authorities may get involved, leading to investigations and possible punishments. This could also make Harry more determined to prove Draco's wrongdoings, driving the plot forward as he searches for evidence. It might also lead to a change in alliances. Some characters who were neutral might now side with Harry out of sympathy, while others might be swayed by Draco's family influence.
Well, depending on the context of the fanfiction, Sirius could also be very understanding. If he knew that Harry and Hermione were just having a private conversation about important matters like their fight against Voldemort or schoolwork, he might just give them a knowing smile and say something like 'Carry on, then. Just making sure everything's all right.' He's a rather perceptive character, after all. And he trusts Harry a great deal, so he would likely give them the benefit of the doubt before assuming anything untoward.
He could be more empathetic. Sirius has a big heart, and being around him, Draco would be exposed to his way of caring for others. This could make Draco more in tune with the feelings of those around him, whether they are pure - blood, half - blood or muggle - born.