Not much further along you'll bump into two frogs that were ran out of their clinic and Curly brace who got sent here as well. I'd personally save the Polar Star for the third and final trade offer soon.
In fact, the store clerk inside offers a nice proposition, if you let him look at your Polar Star and Fireball, he'll combine the two weapons into the Snake, a short ranged weapon that can penetrate walls.
Although the ones inside this little building here are friendly.
Make your way through a few more sliding blocks and you'll get into the real meat of this place, Bug Soldiers and all. For a little bit of fun, see if you can fall all the way down to the ground without hitting any of the floating platforms! Cave Story Walkthrough - Cave Story 71 Reach the top and interact with this computer console to open up the door down the bottom. Take that 'never get free' as a challenge and start to climb upwards taking out the annoying purple blobs. You'll wake up in what you're told is the dump of the island, where all the trash gets sent. You can jump to nearby pages of the game using the links above.