Monster World IV is an adventure platform game, released exclusively in Japan for the Sega Mega Drive in April 1994. It is the sixth and final game in the Wonder Boy/Monster World series.
The story involves a young girl named Arsha, who upon hearing spirits whisper on the wind pleading for help, embarks on a journey to find and aid them. Along the way she becomes master of a genie and adopts a small monster she names Pepe'.
Gameplay revolves around walking along a 2D landscape fighting a variety of monsters, as well as interacting with various people. Playing the game also requires Arsha to utilize Pepe's abilities; such as clogging a lava geyser with his flame resistant body.
While this was viewed as another sequel to the Wonder Boy series, it remains solely as part of the Monster World series, as it was only released in Japan. Still, some games from both series overlap, therefore allowing for some continuity; one example is a book in the Royal Rapadagnan Library that mentions the disappearance of Shion, the playable character from the last game, stating that a large hole appeared next to his house and he was never seen from again. There is also a book entitled The Magic of Eleanora, the Fairy Queen of Alsedo from the last game.
Source: Wikipedia, "Monster World IV", available under the CC-BY-SA License.