During chapter thirteen, when you first get to the bridge, there will be three huge zombie-looking things. Equip the upgraded Dabilahro, stand on the bridge itself and hold down the Y button, charging your Ultimate Technique. Wait for the enemies to get close enough to hit, and then let the Y Button go to unleash your Ultimate Technique. It’ll take a few of those to kill them, but they drop a large amount of Yellow Essence worth about 700 small Yellow Essences. Once you’ve collected them all, go through the door with the blue circle on it, and go through it again to get back to the bridge. The enemies will reappear, so you can do this over and over again.