Or.... who cloned who, exactly?
This game (developed by Epic/Sony) caught my eye when I saw several screenshots of it in Famicom and Game Boy magazines from mid-late 1990. It was clearly an action-RPG modeled after The Legend of Zelda -- and it was even made a full three years before Link's Awakening on the GB!
The title means "Castaway Boy Keith", and you obviously play Keith, a young adventurer set adrift in the South Pacific who winds up marooned on a small island called Harrods Is. To overcome the devil king Drakhe, Keith has to assemble musical notes, for it's music which will ultimately defeat him. (Well, all this sure sounds awfully similar to the plot to Link's Awakening, doesn't it?)
Keith gets advice and purchases items from what looks like Doraemon but is actually a tanuki (Japanese raccoon dog in folklore, folks), and meets old wise men, as per the usual RPG quest. The graphics look quite blocky and tiled compared to more modern ARPGs like Neutopia and Link's Awakening, but they're passable for a 1990 GB title. All the usual things are here as well: heart meters, sub-screens, dungeons, items to collect, and a map to explore. If it had come out in November 1990 as planned, I'm sure we all would have had great fun delving into the mysteries of this Zelda derivative. Now, just why was it cancelled?
Here is yet another action-puzzle game for the GameBoy. Slated for December 1990, it seems to have never gotten a release. Its graphics might look a bit similar to the Natsume-developed Tail Gator, but they seem to share little else in common, game-wise.