Ganso Jajamaru Kun (J) [M][!] is a WonderSwan platformer game likely based on a pre-existing franchise. The [M] suggests a multiplayer mode, and the [!] might indicate additional gameplay features. Ganso Jajamaru Kun could potentially involve classic platforming challenges, collecting items, and navigating various levels.  The exact gameplay style and story would require further research into the source material and the specific WonderSwan release. Information about the developers and publishers is unavailable without more research.

Ganso Jajamaru Kun (J) [M][!]

From TV Animation - One Piece - Mezase Kaizoku Ou (J) [M]