Chaos Zero Nightmare is a free-to-play RPG for iPhone that plunges players into a haunting dark fantasy world. The game is set against the backdrop of a cosmic disaster known as 'Chaos,' which introduces a black fog that engulfs planets, altering their environments and inhabitants. Players embark on a journey aboard the SS Nightmare, encountering strange creatures and uncovering mysteries that challenge their perceptions and decisions.

The gameplay revolves around unique card mechanics and branching story choices, allowing players to shape their experiences. Each session is distinct, with evolving save data that reflects the player's journey through the chaos. Stunning 2D illustrations and dynamic animations enhance the storytelling, complemented by professional voice acting that brings the characters to life, making each interaction memorable.