Gen/Leo fails to save a woman, angering her lover. He must train to defeat the new threat.
A MAC space station member, Officer Shiraido, has come to earth to spend time with Gen and his girlfriend, Yoko. They are attacked by Alien Karly, who grows giant and her. Leo fights the alien, but is defeated, and Shiroto is furious at both Gen and Leo. He decides to patrol himself.
Later, on patrol without permission, Shiroto runs into the alien. He drives it away and discovers its weak spot: the eyes. Captain Dan sends them out on patrol. Gen trains hard, learning a new technique to defeat the alien, who takes out two MAC members.
Dan goes to aid Gen in his training. It is interrupted when an the alien grows to its large size and begins to rampage. Shiroto attacks it, but is buried under the rubble. Just then, Gen arrives and transforms into Ultraman Leo, saving the MAC member.
Leo battles the kaiju, and manages to defeat it by ripping out its horns and jamming them into its head. Shiroto then leaves back to the space station. Gen continues to train the children in the end of the episode,
- Alien Karly (First and only appearance)
Ultraman Leo Volume 2 features episodes 5-8.