Tuna is 100% feral. He has lived indoors since he was a kitten but is basically a ghost...you might see flashes of him on occasion, and he enjoys moving his water bowl around, so you will have small reminders of his existence.
Tuna coexists with people and other pets with no problem as long as no humans reach for him. He does like having animal companions and is also curious about children. Adults scare the daylights out of him. We suspect an adult may not have been kind to him when he was a very young kitten.
He is litter box trained, although he has a habit of kicking litter out of his box and then pooping in the pile he has made just outside the box. We simply keep a large plastic tray under his litter box for easy cleanup.
Thus far, Tuna has been uncooperative for vet care and will bite staff. He is up to date on vaccines and healthy at this time, but your vet should be aware that he must be sedated in his carrier like a feral cat prior to handling.