|Decisive Battle! The Great Sea Monster (Part 2)|
|Kanji||決定的な戦い ！偉大な海の怪物 (その 2)|
|Romaji name||Ketteiteki na Seni! Idai na Umi no Kaibutsu (Sono 2)|
|Decisive Battle! The Great Sea Monster (Part 1)||Decisive Battle! The Great Sea Monster (Part 3)|
After retreating back to HQ, Jun sees Aila in her dream again where she confirms that the monster from yesterday was the force that destroyed Mu, the Dragonsaurus. Jun wakes up and in the morning explains what she saw in her dream. Prof. Nonaka acknowledges the possibility while everyone else is surprised that they actually went to Mu. Everyone tells Jun to go back to sleep so that they can find a way to defeat the Dragonsaurus. An assistant comes in telling everyone that a coast guard boats investigating a mysterious antenna that is guiding the Dragonsaurus were sunk. Nonaka decides to send Hikaru with the Marine Blue Mobile while Sayaka and the Great Booster will be on standby as the other flyers are still damaged from battle. Jun is commanded to contact Aila again in her dreams.
The antenna is being guarded and guided by the Mechanical Beast Rayas D5. Hikaru in the submarine spots it confirming Dr. Hell as the culprit. When Sayaka is ready to destroy the antenna but it submerges and Zarigan G8 attacks. Sayaka and Hikaru fight their opponents who manage to avoid their attacks but they are at a disadvantage. Prof. Nonaka sends Venus A to bring the completed Diana A to even the odds. To buy time, Sayaka has Aphrodite A dive into the water. Sayaka tells Hikaru to get into position despite the big disadvantage she is in. Hikaru reluctantly does so. When it looks like Aphrodite is about to be finished off, Hikaru in the Diana A Marine Blue Mermaid comes to the rescue taking out the Rayas. Diana then fights against Zarigan, using the Exceed Spear's Blizzard Smash function restricts the Zarigan Diana finishes it off with the Trident Missile. However, Dr. Hell speaks over a radio signal telling them that the Dragonsaurus is on its way to Kagoshima, mockingly challenging them on what to do next.