Long time ago, an evil cosmic entity known as Geios was defeated and sealed for aeons. However, a malevolent alien race has found a way to harvest its power and is now preparing for its reincarnation. Pachinko Planet was attacked, and its king slain. Returning from an interstellar travel, Pachio-kun boards the spacecraft Sledgehammer and embarks on a journey to defeat evil and restore his homeland.

Pachio-kun: Warau Uchū is a pachinko game with a storyline and limited top-down exploration. In most areas, Pachio-kun has to complete one or more pachinko games in order to be able to leave the location and advance the plot. Pachinko machines come in different flavors and difficulty levels. The controls are fairly simple, requiring the player to adjust the strength of the shot; the shots themselves can be fired automatically. The game was shipped with a special controller similar to a real pachinko device.