Acquiring the Moons Tear
The path through the sewer is fairly straightforward. There is a Skulltula that can impede your path, defeat it with a few bubble blasts after its back has been exposed.
At the end of the hallway is a balloon blocking the ladder, pop it with a bubble blast. Break the pots and climb the ladder to find Pierre the Scarecrow .
Bypass him for now and instead ascend to the top of the stairs where you can speak with the old man; agree to use the telescope. Look to the top of the Clock Tower and zoom in on the Skull Kid.
Here you’ll see the moon and then a Moon’s Tear will fall just outside. Exit via the nearby door and acquire it, now head back to South Clock Town.