Mio is a co-op game where the players takes the role of a friend of Mio from the book Mio My Son by Astrid Lindgren to help Mio defeat Knight Kato. All the players uses the same pawn, and that is a pawn of Mio. The game has a board with 9 locations, including start and last location (Kato's castle) on it, and paths between those locations with 2-9 steps to walk. On top of the board is also places for 5 courage and 5 stonehearts.
The game play has four phases:
1. Mio moves.
2. The player does actions.
a) travel.
b) regain health or courage.
c) pick up / change various protections.
3. You check if something bad or good happens (some steps on the paths are black, while most of them are white).
4. A cleaning phase where also Kato gradually gets stronger and stronger.
The game ends either when the players manage to take Mio to Kato's castle and defeat him, or when Mio loses all his courage and it has been replaced by Kato's stonehearts.