Jacob could also work as an inside man. Imagine if he infiltrated the vampire world on behalf of the werewolves. He could be trying to find out if the vampires are planning an attack on his pack. Since he has some level of interaction with the vampires already, he could use that to his advantage.
Aro could be an interesting inside man. He's a powerful vampire in the Twilight series. If he were to pretend to be on the side of the Cullens while having his own hidden motives, it could create a lot of drama. He could be secretly plotting to take over their territory or gain access to some special power that the Cullens possess.
An original character could be a great inside man too. For example, a vampire who was exiled from his coven and now wants to get revenge. He could pretend to befriend other vampires in the Twilight world while actually planning to bring them all down from the inside.
It could be a new character entirely. Maybe a young vampire who was turned recently and is still adjusting to the 'alive inside' state of being undead. This character could struggle with the morality of being a vampire while also trying to fit into the Twilight world's complex social structure.
Another option could be Jacob. As a werewolf, he has a connection to the spiritual side of the Twilight world. He might be the one to discover the hauntings first and have to figure out how to deal with them, especially if they pose a threat to his pack or the people he cares about in Forks.
It could be a rogue vampire. You know, in the Twilight world, there are vampires who don't follow the Cullen's rules. This 'man behind the mask' might be one of them, lurking in the shadows and causing trouble for the main characters.
It could be a new character created by the fanfic author. Maybe a young vampire or a human with some special abilities that are related to the Twilight lore.
The main characters in 'inside and out twilight fanfic' are probably Bella Swan, Edward Cullen, and Jacob Black. Bella is the human girl who gets caught in the middle of the vampire - werewolf conflict. Edward is the vampire who falls in love with Bella, and Jacob is the werewolf who also has strong feelings for her. However, the fanfic might also introduce new characters or focus more on secondary characters from the original story like the other Cullens or members of Jacob's pack to show different sides of the 'inside and out' concept.
One idea could be that the 'inside man' is a vampire who has infiltrated the human world in the Twilight universe for a secret mission. Maybe he's trying to find a way to end the conflict between vampires and werewolves without the knowledge of either side.
One great 'inside out twilight fanfic' could be one that explores the emotions of the Twilight characters in a new way, like how Bella's love for Edward might be represented by the different emotions in Inside Out. Maybe there's a fic where the characters from Inside Out are observing the Twilight world and trying to make sense of the intense relationships.
Well, 'inside and out twilight fanfic' might focus on different aspects of the Twilight universe. It could be that it examines the characters from a new perspective. For instance, it might look at how Bella's human side and her experiences as a vampire later on are more deeply explored. It could also show how the Cullens' family dynamics work both within their family unit and in relation to the outside world of Forks and the other vampires. It might even introduce new storylines that are centered around these ideas of what's inside the characters and how it affects what they do on the outside.
Edward could also be the main character. He has his vampire senses which could help him analyze the bloody fingerprints in ways humans can't. He might be on a mission to protect Bella and the rest of his family from whatever danger the fingerprints signify. Maybe he suspects that it's a new threat from a nomadic vampire group and he has to use his skills to track them down.
Maybe it's a side character from the original Twilight books that the writer decides to give more depth to. Like one of the lesser - known vampires in the Volturi coven who has a secret past and motives that are explored in the fanfic.