After you defeat Mack and get the Cricket Pie for Mallow's grandfather, you venture into the Kero Sewers.

Kero Sewers Location

Before you go to the Kero Sewers, you might want to buy some Able Juice in Mushroom Kingdom. You can reach Kero Sewers after you defeat Mack by going southeast from the Mushroom Kingdom.

Explore the Sewers

After the cutscene, use the save block in the corner, then go southeast and swim in the water. Go east, then northeast, and swim into the shallow area of water. You can only jump out of the water from the shallow area. Jump out of the water and read the note if you wish. It explains how to enter pipes.

Go down the nearby pipe. From there, southwest along the bricks to find another pipe. Go down it.

You arrive on a pipe in the north corner of the room. You will see Rat Funks walking around in this area. If you battle them, you might also encounter Hobgoblins, or Shadows. Hobgoblins might drop Pure Water, which you can use to instantly defeat ghosts, such as Hobgoblins and Shadows. Go southeast to find another pipe. Go down it.

There are several Rat Funks in the hallway northeast of where you arrive. Fight your way northeast past them, then go east to the pipe and go down it.

In this area, there are a couple of Big Boos. If Mario is facing them, they cover their eyes and stop moving. If Mario isn't facing them, they will float slowly toward Mario. Go northeast, then southeast to a pipe. Hit the treasure chest to get a Starman, then quickly go down the nearby pipe.

Go northwest, then southeast to find a chest that contains a Fire Flower. Then go back to the north corner of the area, and from there go to the east corner. If you are ready for a battle, hit the chest to fight a Pandorite. It is immune to Mallow's Thunderbolt and Mario's Fire Orb, but is weak to Mario's Jump attacks if he has the Jump Shoes equipped. After you defeat it, you get a Flower Jar and a Trueform Pin. The Flower Jar refills all of your Flower Points and increases your maximum FP by 3. The Trueform Pin prevents the wearer from being turned into a Mushroom or Scarecrow.

From the chest, go southwest, then northwest to a pipe. Go down it.

Go southeast into the water, then go to the northeast and swim into the middle of the northeast wall to go to the next room. There is no place to jump out of the water here, so swim northeast again to the next room. Then you can go northeast to the different color bricks and jump out of the water. Go southwest and go down the pipe there.

In this area, go east until you can jump onto the narrow northeast ledge. Go southeast to where the Rat Funk is blocking the way. Defeat it, then go southeast to the easternmost pipe.

There are many Big Boos in this area. These won't stop moving if Mario is facing them. Go west and up the stairs, then go east and ignore the spring, then jump onto the big floor switch that has an exclamation mark ! on it. Be warned that if you go west and use the spring, you will exit the area and the drained water will reappear, so you will have to come back and step on the switch again to drain it.

From the switch, go southwest and go down the pipe. Now that the water has been drained, you can go southwest from here to the pipe in the south corner, which had been underwater. Go down the pipe.

Go northeast. There is a treasure chest up above, but you can't reach it right now, so just keep going northeast and hit the chest there to get a Mushroom. Then use the save block to save the game, then go southeast and use the pipe there.

If you want to go back to a previous part of the sewer, you can jump onto the spring. Otherwise, equip the Trueform Pin on Mario or Mallow if you got it from the treasure chest monster earlier, then talk to the creature to the northeast. After a cutscene, you will battle Belome.