The third yellow crystal is on the other side, but sadly out of reach. Chococat suggests asking My Melody for help, who’s waiting inside her house. Be sure to bring two Strawberry Crates with you.

These little yellow crystals have no description and give you no hint on how best to use them. This page explains what Energy Crystals do in REPO and how to use them.

At service stations in REPO, you’ll see energy crystals. We explain what these expensive yellow crystals do and how to use them.

To find the second yellow crystal, start from Badtz-maru's shop and head north, ... There, you’ll find a deep underwater pit. Dive in, and you’ll discover the first crystal.