Yukiide Kaoru (雪井出 薫) was diagnosed at twelve with encephalitis lethargica or "Sleepy Sickness". Due to this sickness, he lost ten years of his life in a coma. He awoke, completed changed and enslaved by his father's ideals of order.
As Yukiide explains it, the purpose of this game is to fill in the gaps of his memory. It is not only that, however, as the loser is pinned with a serious crime upon losing, with no evidence to the contrary.