From Yen Press:

A young man, driven by jealousy over love, tells a lie that accidentally results in the death of his older brother. Some time later, Hiro is kidnapped and confined to a room with eight other people, each wearing a grotesque animal mask. Their kidnapper informs them that their time has come to be judged for their "sins"-and that they will have to judge one another. Every twelve hours, the captives must choose who among them will die...and only four will remain alive when all is through...