An important character with a lot of lines, is fused with Ash (a main character) so i guess you could consider her a main character by association.

Shares Ash's body after they fused, she can take over ashes body however mainly lets ash get on with her life and is happy to talk to ash in her head.

She really enjoys humming and has a song stuck in her head but cant remember where she heard it from before. 

Like "shitface" the more upset or angry she gets the more her voice distorts

Unlike Ash she is fairly outgoing and happy to start a conversation with almost anyone. Shes a bit of a trouble maker and a prankster, she loves to scare people. 

Her voice is different from Ashes and when she takes control of Ashes body she can ether use Ashes voice or her own, but mainly chooses her own voice so she doesn't accidentally do something to get ash in trouble. 

She is good at judging characters in most people, but for those she cant judge it makes her uneasy and try to avoid all contact with them if possible. 

Wanderers are people who were killed in their life ether in a brutal way or before they should of died, They are trapped in a dark shadow realm that's connected to earth. They can travel between the realms but cant be seem by most people or interact with the physical earth for the most part. To move on and finally be allowed to rest in peace they must discover whats tying them to the earth still and then must (depending on whats keeping them tied to the earth) destroy the object, see justice done if someone killed them or watch a family member grow old and get on with their life until their death. 

Kara used to desperately search for the answers she needed to find to finally rest, however after meeting Ash shes decided that for now she is happy the way she is. 

There is more information on the wanderers in the description of this reference sheet 

https://www.deviantart.com/its-a-paco-thing/art/Ash-ref-784026782