Wonder Boy in Monster Land, originally released as Wonder Boy: Monster Land in Japan, is the direct sequel to Wonder Boy. Developed by Westone and published by Sega for Sega System 2 hardware, the game ditches the left-to-right platforming gameplay of its predecessor in favour of a platform-RPG hybrid gameplay style. The original arcade version was only released in Japan, though was planned for an overseas release.
You play as Wonder Boy as he explores various short levels filled with respawning enemies. The control panel has two buttons: one to attack (with a sword you get in the first building you visit) and one to jump. enters buildings. At the end of each level, you have to enter a building to fight a boss, whose defeat will unlock the exit. There is a timer on the bottom left of the screen; if it runs out, you lose a heart. Run out of hearts and you lose the game. You gain full health after clearing a level.
In Japan's 1987 Gamest Awards, it came eighth place in the "Best Ending" award category. 
Wonder Boy in Monster Land was later ported to the Sega Master System and released to all regions. In Japan, this port is known as Super Wonder Boy in Monster World (スーパーワンダーボーイ モンスターワールド), beginning the Monster World naming trend that would eventually replace Wonder Boy as the series's name in Japan. In Brazil, the game was renamed Mônica no Castelo do Dragão, with characters being taken from the Brazilian comic series Turma da Mônica, also starting a trend of renaming Wonder Boy releases to tie into the show.
The game saw the most success on the Sega Master System, though it was also brought to the Amiga, Atari ST, Commodore 64, TurboGrafx-16, and ZX Spectrum by Activision as Super Wonder Boy. When Hudson brought the game to PC Engine in Japan, the game was renamed Bikkuriman World and replaced some of the characters with others from a then popular sticker collection, which had just been turned into an anime.