In some fanfictions, it could be because Draco shows a different side of himself. Maybe he protects Harry from other threats secretly. For example, he might use his knowledge of the Slytherin world to keep Harry out of danger.
One reason could be that in this fanfiction, Snape has some hidden kindness towards Harry that he doesn't show in the original story. Maybe he secretly protects Harry from other threats, which makes Harry feel safe around him.
One common scenario is when they are in a dangerous situation together, like facing a powerful dark wizard. Draco steps up and uses his skills and knowledge to keep Harry safe. For instance, in a fanfic where they are trapped in a haunted castle, Draco uses his Slytherin cunning to find an escape route for both of them, which makes Harry feel protected.
One specific moment could be when they are in a dangerous situation, like facing a powerful monster, and Percy steps in front of Annabeth to protect her. His confident stance and the way he holds his weapon makes her feel safe because she knows he'll do anything to keep her from harm.
One possible reason could be that Snape has shown unexpected kindness to Hermione in the fanfiction. Maybe he has protected her from some danger secretly, which makes her feel she can rely on him and thus feel safe.
In the original series, Harry and Snape have a very tense and often hostile relationship. But in this fanfiction, their relationship is likely to be much more positive. Harry feeling safe with Snape means there is a sense of trust that was absent in the original.
Another possibility is Dumbledore. In some fan - created stories, if Dumbledore was found to be hiding crucial information about Harry's past or destiny for his own purposes, Harry would surely feel betrayed. After all, Harry had put so much trust in Dumbledore as a mentor.
Harry may also get angry. He could lash out at the person who he believes has betrayed him. For instance, if it was Ron, he might shout at him and say things he doesn't really mean in the heat of the moment. This anger would be a result of his deep - seated hurt from the betrayal.
In the original series, Snape is often quite harsh towards Hermione. However, in this fanfiction, the relationship is completely different. Here, Hermione feels safe with Snape, which is a huge deviation as in the original, she would be more likely to be on guard around him.