Dark Cloud Acquiring Goro/Second Dungeon Territory 9
Much like in the first dungeon, the Divine Beast Cave, you have to acquire a controllable character in order to proceed forward once you reach Territory 9 in the Wise Owl Forest. This time you need to acquire the fat guy you may or may not have dueled around the time you arrived in the second town. To unlock Goro you must do a few different things:
1. Beat Goro in a duel
2. Connect the river from the waterfall to the tree
3. Complete Cacao's House and obtain the Odd Tone Flute
4. Use the earrings obtained from beating Goro in the duel to talk to the tree in the forest to obtain the Serpent's Sword
5. Use the Odd Tone Flute to summon the snake in the Wise Owl Forest and use the Serpent Sword to duel him. Take the Necklace he drops back to Goro to become his BFF
The steps are in the order you'll most likely do them in. In order to do step 5 though, you'll need to have done all previous steps which will allow you to duel the snake in the forest (and win). Once you have beaten the snake you take the necklace to Goro, watch a scene and that's really all there is to it, he's yours to control after that.