Three of the biggest super robots ever made on one screen at once, doing what they were built for: smashing things that need smashing. The plot is a clothesline to hang giant robot fights on, and it knows it. If you grew up on 70s mecha or you're chasing that specific flavor of cheesy, straightforward destruction, this is what peak novelty looks like.

A giant sea monster called Dragonsaurus appears without warning and spreads terror through the depths of the ocean. To stop it, Great Mazinger, Grendizer and the Getter Robo G team unite against the new danger. Their mission grows harder when the creature swallows Boss Borot and sets its course for Tokyo. The film is a mecha adventure that brings together three giant robot franchises for a single battle against a monster from the sea.