Vivian (Surname TBC)

Fantasy world: 

Vivian was born in a coal mining town and studied at a magic school (mostly navigation-based magic, but also other areas) because they wanted to help out their father in the mines (the town was pretty poor due to greater popularity of mining magical ore, but had a close-knit community Vivian felt they were a strong part of).

However one day a mining accident happened because of coal dust igniting and it caused the deaths of some miners, it also caused Vivian to lose their arm and also develop some permanent burn scars. Some members of the community were very anti-magic and started spreading rumours that Vivian caused the explosion, and as a result Vivian was essentially ostracised from their own hometown by these rumours, and so left to find work elsewhere (and sending money back to care for their father).

The only line of work Vivian felt they were useful in would be sky sailing, due to their excellent magical navigation abilities; they developed this realisation after going through dull, menial jobs (such as working in a library), but on the side they were studying magic (by reading the books in said library, notably).

And so they eventually joined a merchant ship crew as a navigator's apprentice, but down the line the crew were attacked by sky pirates. The pirates kept Vivian alive, because of their navigational skills (also by this time they had learnt how to replace their lost arm with a magically-conjured one), whereas the other navigator had been killed in the attack.

The crew were fairly hostile and unfriendly towards Vivian, which caused them to begin to look for ways to escape.

One night in a tavern, while docked at a small port town, they came across Christopher, another sky pirate captain of a different crew; Christopher, using his sly charm, convinced Vivian to join his crew, and so Vivian found a way to escape their previous treatment.

However, Vivian began to realise that Christopher was not charming towards them out of affection, but out of a way to get them on his side-- this realisation that Christopher did not value them as much as Vivian valued him hurt them greatly, as they had spent many months pining after him after being recruited (as a result of his flirtatious behaviour). Although, on the plus side, Vivian had began to make close companionships with their fellow crewmates.

Tension reached an all-time high when captain Christopher planned a heist on a giant casino airship. During this attempted robbery, Vivian stood in the way of Christopher, trying to stop him from continuing with this. Christopher attempted to disarm them in order to get Vivian to stand down, but the skirmish resulted in Vivian slashed open by his sword. In retaliation, Vivian lashed out with a jet of flames, which spread and not only blocked the way, but set the casino on fire, and the crew were forced to evacuate.

As Vivian lay dying, they were rescued and revived by the crew of a privateering (pirate hunting) ship, lead by captain Lunette, who did this to get answers out of Vivian. Since Vivian was now in debt due to the cost of healing them, they decided to join this crew in the hunt for Christopher.

In the end, they find his ship, and Vivian enacts revenge by stabbing him through the chest, setting his cabin on fire, and leaving him to die. Vivian spends the rest of their days on Lunette's crew, now happier and a close confidant to her as well as friends with some of the other crewmembers.

Modern world:

Vivian is a uni student studying veterinary medicine as a degree. They are friends with Zander, a fellow vet student, but they also share an interest in cryptozoology (and just zoology in general) with Nadia. One day they find Nova, a demon, in the local forest, and try their best to steer people away from finding out about them. When Nadia, Christopher and Sasha (all friends in this modern scenario), attempt to go into this forest to find a 'cryptid' that has been rumoured to roam the area, Vivian fakes running up to them all shaken and scared in an attempt to steer them away. However, this causes Nadia to be even more intrigued, and tries to interview Vivian on their amateur online radio show. Nadia is determined to find this cryptid, and so drags her friends and Vivian once more into the forest, trying to use Vivian to guide them to where they saw it.

However, it turns out there is another demon/creature other than Nova roaming the forests that attacks/chases them, and Vivian ends up leading them to Nova's hiding place for safety, wherein the group of friends discover Nova. At some point, Vivian takes them to their house, where they have a board in their room full of ideas and theories on how these demons have been getting into their world, and how to close this rift that has been created.

Side note: Vivian and Christopher have a chilly relationship, as they used to be friends but fell out in highschool.

[I have more to add to this, but it would be derailing to talk about the entire plot, rather than just Vivian's side, but essentially this group are trying to get to the bottom of this demon-business.]