Project X Zone is a crossover tactical role-playing game for the Nintendo 3DS. The game is a follow up to the video game Namco × Capcom and features characters from Namco Bandai, Capcom, and Sega. Stages in Project X Zone take place in grid-based locations from the game's many crossover titles. Each friendly unit is made up of two characters (thus referred to as a Pair Unit), though a third character (or "Solo Unit") can be added for once-per-battle assistance. Unlike Namco × Capcom, units can move freely within their range on the field map, with no penalty for accessing treasure chests or destructible objects prior to attacking.

The year is 20XX AD.

The world is in the middle of a quiet chaos.

Shadows lurk behind the unchanging peacefulness of everyday life. Twisted beings writhe unseen in the darkness. Mysterious dimensional portals connect the real world to others more fantastic.

But with the passage of time, people eventually have come to understand and even accept these things as part of their daily lives. All without knowing of the existence of the people and organizations fighting the true evil.

The Kouryuji Estate------ There is a certain family that has worked in secrecy behind the scenes throughout history. This story begins with the theft of a treasure known as the "Portalstone" that this family has been protecting over the ages.

Mii Kouryuji has enlisted the help of private detective Kogoro Tenzai in order to locate the stone.

Who stole the stone? And for what purpose? The thoughts and ambitions of various people, organizations, and mythical beings mingle and eventually the case becomes a chaos of a grand scale.

The worlds of the past, future, and even dimensions become involved.

Thus, our heroes' long journey is about to begin.