Asahi and her friend Yamato went together to an exclusive event as test players for a new game from the cellphone-game company "Sky Nova." The test players were a diverse lot of all ages, from ordinary teens like Asahi to popular idols. The company took all of them on a cruise to explain the rules of this island-based, treasure-hunting survival game. Suddenly, during the presentation, all of the participants lost consciousness. They woke up on an actual island wearing a strange watch with the words "Game Start." Now they are all stuck in this survival game, which has become all too real and deadly!

(Source: MangaHelpers)