Look up the Etoro Tribe of new guinea or new zealand. (Cant remember which). Their rituals for "coming of age" for boys involve similar practices.
EDIT: Also polyandry is common in other places of the world. Specifically in Tibet.
I doubt the anime would shock me that much. It may be a little odd but certain parts of the world have similar cultural practices so it cant be that bad. Also, i have no soul or code of ethics so i have nothing to lose here. Im not really into cartoons anymore though.