S⁄⁄D/theories

Mark is son of the Rich or adopted by Rich.
Judging by Mansion like location where is paintings of Takashi (Older) and Funetsuki (Tec) Mark can be son of rich or adopted, but judging by moments when Mark using kunais on rich gentleman or lady and then they turn in monsters, steal some effects and teleporting him in unascapable area, its can be that when Mark behaved bad his parents took away his toys and locked him in some kind of detention room.