Developer : Sega / WestOne
Publisher : Sega
Platform : Sega Mega Drive
Year : 1994
Monster World IV is the sequel to Monster World III, which was released on the Sega Mega Drive and Sega Master System in the west as Wonderboy in Monster World or Wonderboy 5 (I think). The game is what would have been called an 'arcade-adventure' in the 8-bit era - it's a platform game with RPG elements (combat, stats, an inventory and a chapter-based story).
The protagonist is a girl called Asha, who starts off in an 'Arabian Nights' style land and has to fight and explore through a diverse series of dungeons and towns. Quite early on in the game, you discover an egg which can be hatched into a flying pet (which looks kind of like a Rabbite from Secret of Mana) which can be used to help you reach previously inaccessible areas.
Monster World IV is a masterpiece of game design. The graphics are deceptively simple and child-like, but boast detailed animation and dozens of neat ideas. (For instance, the playing area is given a small amount of 'depth' by allowing you to enter buildings, which can be many 'layers' deep.) The game slowly introduces you to each new feature before chucking you into a new dungeon or wilderness fraught with extremely challenging obstacles.
The graphics are varied and very solid-looking (this looks more like a SNES game than most MD games) and the sound is great too (with many variations on the main theme tune).
Like Firelord on the ZX Spectrum, this is a really finely crafted piece of software and one which I wholly recommend. (The Japanese text doesn't hinder the gameplay overmuch as long as you can work out how to save your game! It's all pretty self-explanatory.)
It is possible that this game did get released in the US. Since playing the Japanese version I have seen screenshots of an English language version online.