After you make it through the first cave of Chapter 6, you battle the Giant Turboss.

How to Defeat Giant Turboss

Jump onto the southeast tile to make an Anklet appear. Take it and you will be able to reach the northwest and northeast tiles. However, it's easier to dodge the bubbles that Giant Turboss shoots out at you if you stay on the southern tiles. Wait for Giant Turboss to move south to where you can hit it, and quickly jump to where it is, or to one of the northern tiles, and hit it as many times as you can before it moves back north.

Moving On

After you defeat Giant Turboss, go west through the door and you will reach part 2 of the cave.