Character Design - Captain Character Back-story

I started off with coming up with a background story for my character, which will influence the aesthetic of my character greatly.

I came up with the imaginative backstory that my character can see ghosts, but not in the macabre sense for a change, this has been done too many times, in a humorous sense. A character that loves the ghost world even more so than the human one, they "mingle with the afterlife", someone that is a big deal, confident and outgoing in the ghost world, yet sensitive and shy in the human world. However having such a close attachment to the world of the dead has driven them a bit crazy, which should be present in their appearance.

From there I thought, they could volunteer in a charity shop! Because there is a chance the dead could attach to their previously owned clothes, giving the character a chance to mingle with the dead whilst working. My character could work part-time at the charity shop whilst studying a degree, a degree in psychology as they long to understand the psyche of humans, and maybe to figure out an explanation to the fact they are on the same wavelength as the dead.

All these points considered I feel my character would be better suited to being male, and because of the degree, around the age of 20.

However I feel he should look older than 20 to expose how seeing the dead has had an effect on his mentality, how the stress of it when he was little has aged him somewhat.