has been largely ignored by many due to the Japanese text, but finally a proper English version was recently released and made available for download. This translation is much better than the one that has been making it's rounds, with most of the storyline kept intact and understandable.
The game itself is a nice little underwater exploration number that won't take more than an hour or two to solve. Fans of Cave Story certainly wouldn't be disappointed with one of Pixel's earlier work.
A partial walkthrough can be found in this forum thread