One possible plot could be that Hermione, in the guise of 'little red', encounters Fenrir in the Forbidden Forest. Maybe she's on a mission related to some dark magic research and Fenrir senses her presence. Their encounter could lead to a battle of wits as Hermione tries to outsmart Fenrir to escape or gain some valuable information from him.
Perhaps in this fanfiction, 'little red hermione' is a new form of Hermione that has emerged due to some magical accident. Fenrir, being a werewolf, is initially drawn to her out of curiosity. The plot could revolve around Hermione trying to find a way to reverse this change while Fenrir is both a threat and an unexpected ally at times, as they both have to deal with other dark forces in the wizarding world.
One possible plot could be the challenges they face. Maybe Hermione is initially scared and conflicted about the pregnancy as Fenrir is a complex and somewhat dangerous character. Society might not accept their union, so they have to deal with secrecy and the judgment of others.
Obviously, 'little red hermione' and Fenrir are the main characters. 'Little red hermione' is a unique take on Hermione, perhaps with different abilities or a different personality in this fanfiction. Fenrir, with his werewolf nature and his own motives in the wizarding world, will have a complex relationship with 'little red hermione' as they meet and their stories intertwine.
One possible plot could be that Fenrir, for some reason, has a change of heart. Maybe he sees Hermione's kindness and intelligence during one of his encounters with the wizarding world. He starts to protect her secretly from other dark forces. And Hermione, initially afraid, gradually realizes there's more to him than just a monster.
One possible plot could be that Hermione stumbles upon Fenrir Greyback in a situation where he's about to be killed by some dark wizards who see him as a loose end. Hermione, being the empathetic and brave witch she is, decides to save him. Maybe she believes that every life is worth saving, even a werewolf like Fenrir. She could then try to rehabilitate him, using her vast knowledge of magic and her strong moral compass.
One possible plot could be that Fenrir Greyback, for some reason against his usual nature, discovers Hermione in a vulnerable state. Maybe she's been separated from her friends during a battle. He decides to keep her safe from other dark creatures, seeing some sort of potential in her that he doesn't want wasted. He might teach her some of the ways to survive in the wild, which are skills he has as a werewolf.
One possibility is that it's a story of redemption for Fenrir. He starts to watch over Hermione and in the process, he begins to see the good in people he's been trying to harm. As he watches her, he might be influenced by her kindness or her intelligence, and this gradually changes his view of the wizarding world and his place in it.
One possible plot could be Hermione's research on werewolves leading her to interact with Fenrir Greyback. Maybe she wants to understand the werewolf curse better and tries to interview him in Azkaban. Through their conversations, she discovers the dark and twisted past that led him to become such a feared and cruel werewolf.
One common theme is the idea of friendship. Despite their different natures, Little Red and Fenrir often form a bond in these fanfictions. For example, in many stories, Little Red's kindness helps Fenrir to be less of a lone wolf.
One possible plot could be that Hermione discovers she has some sort of connection to Fenrir through a magical bond. She initially resists it due to his dark nature but as she gets to know him better, she realizes there is more to him. Maybe she tries to help him control his werewolf side and in the process, they develop a relationship that is frowned upon by the wizarding community.
One possible plot could be that Naruto is somehow reincarnated as Fenrir. He might retain some of his ninja abilities but also gain the powers of Fenrir like super strength and the ability to change forms. He could then use these combined powers to protect the Hidden Leaf Village from a new and powerful enemy that normal ninja techniques can't defeat.