Read manga: Judge

manga
Summary:

Hiro's brother Atsuya is dating Hiro's childhood friend and secret crush Hikari. Hiro's affection for Hikari will lead him to commit an un-punishable crime against his older brother. At least, he thinks it is un-punishable, until he is kidnapped and imprisoned by a group of people wearing animal masks. The judging is about to start! Basicly same principles of "gore Game of concealed murderer" as in Doubt.