A giant sea monster known as Dragonsaurus has emerged from out of nowhere, terrorizing the depths of the oceans. Great Mazinger, Grendizer and the Getter Robo G team join forces to combat the new threat. But their task becomes more complicated when Dragonsaurus swallows up Boss Borot and makes its way towards Tokyo.

Source: ANN

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Same characters: Great Mazinger
Same characters: UFO Robo Grendizer
Same characters: Getter Robo G