Many times, she has a kind heart. Harry has been through a lot of hardships, and a kind - hearted girl would be able to comfort him. She could be the one who volunteers at the Hogwarts hospital wing, taking care of the injured students, and her kindness towards everyone, especially Harry, makes her a likely candidate for his secret girlfriend in the fanfiction.
Often, she is intelligent. In the world of magic, intelligence can be shown in various ways like being good at spells or understanding complex magical theories. This would attract Harry as he himself is quite smart. For example, she might be able to solve a difficult magical riddle that has stumped others, including Harry.
She is usually brave. Given Harry's constant battles against the dark side, his secret girlfriend in fanfiction would need to be brave enough to stand by his side. Maybe she's not afraid to face a dark wizard when protecting Harry or his friends, showing her courage in the face of danger.
Often, she is depicted as strong - willed. Since Naruto is a very determined character himself, having a girlfriend with a similar trait can create interesting story arcs where they support and challenge each other.
Another scenario could be that they start off as friends or classmates and gradually develop feelings for each other without realizing it at first. Then they keep it a secret because they are not sure how the other person really feels or they are afraid of ruining their friendship. In this case, there could be a lot of internal monologues and awkward moments between them in the fanfiction.
It could be a Muggle - born witch who he meets outside of Hogwarts during the summer holidays. She's not part of the typical wizarding society he's used to, so they keep it a secret as it's an unusual situation for a wizard like Harry to be involved with a Muggle - born in such a way.
In some OC fanfictions, it could be a new witch created by the author. For example, a shy witch who meets Harry in the Forbidden Forest while he's on one of his solitary walks. She might be secretly helping him with some of his struggles against the dark forces without him knowing at first, and gradually a romantic relationship develops.
There could be an original character created just for the fanfiction to be Harry's secret girlfriend. Writers often introduce new characters to add new plotlines and romantic interests for the main characters.
Some common original character traits in Harry Potter fanfiction could be having a unique magical ability. For example, an oc might have the power to control the weather within the Hogwarts grounds. This can add an interesting dynamic to the story as it interacts with the existing magical elements in the Potterverse.
In some fanfictions, it could be a character from another magical school. Like a girl from Beauxbatons or Durmstrang. She might have met Harry during an international magical event and they've been secretly seeing each other ever since.
One common theme is the exploration of forbidden love. For example, when a character from a different house or with a different social status in the wizarding world falls for Harry. Another theme is the growth of the relationship through shared adventures, like fighting dark wizards together.
Well, in a lot of Harry Potter fanfiction, Flint is often depicted as a proud character. He takes pride in his Slytherin heritage and his position as Quidditch captain. Also, he can be seen as a bit of a traditionalist, adhering to the old - fashioned Slytherin ways. For instance, he might look down on newfangled ideas or those who don't conform to the strict Slytherin hierarchy as it has been for generations. He is also sometimes shown as having a bit of a temper when things don't go his way, especially in matters related to Quidditch or the reputation of Slytherin house.
In many Animagus fanfics with fem Harry Potter, she uses her Animagus form to break gender norms in the wizarding world. Her form may give her more freedom to move around and be more assertive than a typical female witch in that setting.