I'm... Who? (An IT story)

Pensalia was a normal boy as described in the 1890's at least that is before he disappeared... His full name is Pensalia Jason Wiser(not an OC, you'll figure it out), and he had red-orange hair and bright red eyes with white pupils that are shaped like a cat's. After many years he comes back but no one recognizes him. He was 14 when he died and he still is, well not exactly. He has memories that came from nowhere. He doesn't know what to do anymore and almost gives up until he finds a hidden door in the ground that led to a secret base. It looked like it was abandoned but someone unhooks the latch on the door and light comes in.. who might this mystery person be?

(Sorry I couldn't have a book cover but I will I promise ;-;)