Answer:
First you need to finish chapter 6 then go to merlon's house he will mention a guest that wants to speak to you who is currently there he will tell you to go to shiver city he goes to unlock the door for you now go underground since you have Sushi now go down the hole then swim across the water if you have not already defeated it a Blooper will attack after defeating it continue east until you find a area with a blue door but no way to get across if you already have the tornado boots use them to find secret blocks which create a path for you to get to the blue door if you don't have the boots there is an area where you must use Lakilester to move across spikes if you go through the pipe and continue through the area you will soon find a chest inside is the tornado boots. Open the blue door and go in the pipe go left and use the super block go back to the right and enter the semi-frozen pipe WELCOME TO CHAPTER 7 AND SHIVER CITY!