To sum up what happened; Gorgom's plan succeeded and gathered these humans in one place so that they can harvest Gorgumes with ease. To put it simply, it is one of those Gorgom plans that succeeded. They were able to harvest enough fruit to last for three days. To put it simply, it is not enough to last for one year. But before they can harvest more fruit, Kotaro deducted their possible base of operations and to stop him is the Cactus Mutant. I am not sure why Gorgom went with the Cactus Mutant since Gorgumes needs to grow in a proper environment but what the heck, at least someone will fight BLACK!
The final fight between BLACK and Cactus Mutant is quite intense. BLACK is again on one tough situation because he doesn't know how to defeat him. Thankfully, he remembered Katsumi advice about cactuses that watering them too much will kill them. All of a sudden, BLACK throws the Cactus Mutant in a nearby river. That scene surprised me a bit for the reason that earlier in the scene, we barely see any rivers around and all of a sudden; BLACK throws the mutant in some river that appeared out of nowhere! But what the heck, at least he gets the job done at the end!