Gurumin: A Monstrous Adventure is a 3D platform game with an emphasis on action and platforming with puzzle elements. It stars a 12 year old girl named Parin who needs to move in with her grandfather, the mayor of a mining town called Tiese, as her parents go overseas on an excavation. Parin felt fine about moving in with her grandfather until she hears that she is the only kid in the town and has nobody to play with. Nonetheless her grandfather suggests that she goes exploring the town and stopping by to see Fan, the woman who runs the town bakery, to see if she can be friends with her.
After visiting the shops and exploring what little Tiese has to offer, Parin is surprised to find a girl being attacked by a stray dog. Parin hurries to rescue the girl but quickly finds out that the girl she rescued is actually not a girl at all, but a monster named Pino. Parin is then taken through a hidden entrance near her house by Pino and her brother, Puku, where she meets the rest of monsters in Monster Village and finally finds some friends to play with. Unfortunately, soon after Puku is kidnapped by evil creatures called phantoms and it's up to Parin to rescue him, so the other monsters provide her with the only weapon they have, a legendary drill.
As Parin makes her way through the first dungeon to rescue Puku, the phantoms attack Monster Village which puts the whole world at risk. It is now up to Parin to make her way through more dungeons to restore Monster Village and save the world.
Parin's drill has four power levels that build as she fights, or at restoration points, and the decreases as she receives damage. Parin can also equip accessories that have various abilities such as increasing defense or giving her a larger numbers of coins as she defeats enemies. Coins and junk are two forms of currency in the game that are used to acquire and upgrade accessories or learn new attacks. Coins can be found easily in pots or are dropped by enemies, however junk can only be acquired when dropped by enemies that were carrying an item such as a shield.