- play as an ordinary young man who ends up captured and placed in an ominous, enigmatic situation with eight other individuals
- 'Lying' and 'betrayal' are some of the major themes in this title
- each character has their own beliefs, purpose, and goals
- participate in a complex psychological contest called the Nonary Game
- game is orchestrated by an AI taking the image of a rabbit and referring to itself as Zero III
- each character wears a bracelet
- characters can lose and gain BP (Bracelet Points)
- reaching nine BP lets you attempt to open a door with the same number and escape
- losing all BP means you die
- pick "Ally" or "Betray" with other charactrs
- if both participants choose ally, they each receive two BP
- if one chooses to ally and the other to betray, the former has two BP deducted while the latter gains three
- if the betrayal is mutual, BP for each remains constant
- touch screen-based puzzles
- slide puzzle, a code puzzle, a logic puzzle, a math puzzle, a panel puzzle, a line puzzle, a scale puzzle, a dice puzzle, an hourglass puzzle, a clock puzzle, a cocktail puzzle, a billiard puzzle, a dart puzzle, a jukebox puzzle, a DNA puzzle, a pH puzzle, a jellyfish puzzle, a Zero III doll puzzle, a slightly perverted puzzle, and several others
- warm reception to 999 in the West was the catalyst for the production of Virtue's Last Reward