The 5th Dimension's Jaku Empire has begun their plan to invade and conquer the 3rd Dimension, specifically the Earth. But then one thing stands in their way, and that's Raijin-Oh, piloted by Eldran, who arrives there to stop Belzeb from launching a missile full of Akudama to the Earth. While Eldran is trying to stop the missile, Belzeb attacks Raijin-Oh, who is sent falling to the Earth. The Akudama missile is destroyed, but its contents are then spread out all over the world.
Meanwhile, the 3rd class of the 5th grade in Hinobori Academy is having a class in session. Just before it ends however, Raijin-Oh crashes on top of their class, though all the students are safe. Eldran comes out from inside Raijin-Oh, bestows the medals with the power to control Raijin-Oh upon Class 5-3, restores their classroom to normal (though it can become a command center as part of the things he gave them), and then leaves for a while to rest.
Their first operation comes when the first of the Akudama is activated by finding out what a human dislikes, and becoming a Jaku Beast. Jin, Asuka, and Kōji are sent out in Ken-Oh, Hou-Oh, and Juu-Oh to defeat it. After a while they combine into Raijin-Oh and destroy the monster. This would be the first of many battles waged against the Jaku Empire by Class 5-3, which would afterwards be known as the Earth Defense Class.
- The Jaku Empire begins their invasion of Earth.
- Eldran gives class 5-3 command of Raijin-Oh.