After defeating the first Siren, use Newt Dash to get back to town. A woman with an exclamation mark will point you to the shop on the first floor with a green bottle icon. The first item is east of town, using Newt Climb to get over the wall. Continue on east until you reach the dock, finding the barnacle just past the sleeping person. The second item is west of town, using Newt Dash to clear the distance. Enter the hut at the end, talk to Bolo, and check the trash can.
Turn in the quest for a Fusion Stone, then enter the top right door to talk to Plink and get Seer Dance.
Leave town to the west and drop into the pit, then continue west. When you reach the large gap at the end, use the Seer Dance by holding
and then pressing
to make platforms appears. Continue west to reach Tree Town.