I forgot the title

#1
Well. The story is famous in the site and is about a guy who is immortal, He is really old, like, From 1000 A.D, he fought the 2 WW, he LOVES fries and has a friend/lover who has 2 personalities(?) and wears a face mask made out of human skin(the friend uses the mask), The MC is a strong believer in religion, The MC doesn't use any kind of magic, the way he fights is destroying his own body and regenerating right after ( English is not my first language so sorry about any mistakes in the message)