Greenman vs. Megahertz (グリーンマン対メガヘルツ, Gurīnman tai Megaherutsu?) is the ninth episode of Go! Greenman.
Maoh, once again wanting the blood of children so he can escape the Underworld, confronts Tonchiki on the matter. He presents his master with Megahertz, a moth monster with a blinding stare. While in the process of deploying Megahertz, a child had been at the playground and saw glowing red eyes coming from the Underworld's entrance. He calls over two other kids to look, but they are chased away by the monster who steps out into the open. He chases them up a street, and even grabs one of them. The other two see this and summon Greenman with the Green Calls. As usual, Greenman flies in and lands in front of the monster. He lets go of the child who runs away so he can fight with the now approaching challenger. They jump on a ledge, and up to a small field where they begin to fight. After a short battle, Tonchiki teleports to the site and makes Megahertz grow. Greenman does the same so he has a chance of defeating it. They continue their fighting on a small mountain, where Greenman eventually uses his Fire Fighting attack to trap Megahertz in a blinding smokescreen. However, the monster quickly escapes and returns the favor by damaging Greenman's electronics with its blinding stare. Megahertz was quickly able to beat down the blinded and weakened Greenman. The children realize their hero is in trouble, and use the Green Calls to restore his sight. With his vision back, Greenman picked up a handful of rocks and threw them at Megahertz' face. He then summoned the Greenman Stick and greatly weakened Megahertz until he finally finished it off with a new ability, the "Stick Beam".