Game description from Romhacking.net:
I'm sure most people have played at least one game in the Hudson's Adventure Island series, what with its countless NES and Gameboy games. And because of this, most people will not play this game. Why? Well hell, Adventure Island sucks! You just walk forward the whole damn time! You jump over various things, and that's about it. Fortunately, this version of Adventure Island is actually good. In fact, it's really really good, which makes me wonder why it never was released here. Anyway, instead of merely going straight the whole time, facing nothing more serious than a rock or a slightly steep incline, Adventure Island 4 is laid out in a very non-linear fashion. You could call it a cutesy Metroid or Symphony of the Night, but I wouldn't recommend it. Oh, and the fruit? Those useless things that you did your damnedest to catch every single one of, although they did nothing more than raise your score slightly? They actually serve a purpose here! Yeah, it's cool! For every eight fruits you get, you regain a heart's worth of health. It ain't much, but you don't get hit a whole lot so it all works out. Anyway, it's a great game that I order you all to play.
Unofficial English translation available:
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source: www.romhacking.net