Jiji the Cat continues on his journey to the land of fish from where chapter 2 left off. Travelling deeper into the forest in the hopes of finding the land of fish, he finds a young witch named Katy who has lost her broom. Jiji sets out to help her so that the two of them can travel together on his journey.
Jiji and the Mysterious Forest is the third of three child-friendly RPGs in the Jiji series, and the first to be released under the Katyfraise name. Compared to previous games in the series, it features higher-detail watercolour artwork and presents the game as taking place inside of a storybook. The player directs Jiji using the mouse cursor and selects options from a mouse-driven menu.