

Grendizer, Getter Robo G, Great Mazinger: Decisive Battle! The Great Sea Monster
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
Where to watch Grendizer, Getter Robo G, Great Mazinger: Decisive Battle! The Great Sea Monster in United States
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Click a service to open Grendizer, Getter Robo G, Great Mazinger: Decisive Battle! The Great Sea Monster there. Availability last verified on June 20, 2026.
About Grendizer, Getter Robo G, Great Mazinger: Decisive Battle! The Great Sea Monster
Grendizer, Getter Robo G, Great Mazinger: Decisive Battle! The Great Sea Monster is a 1976 Japanese-language action, adventure and animation film directed by Masayuki Akehi. The cast is led by Akira Kamiya, Hiroya Ishimaru, Keaton Yamada. It has a runtime of 0h 31m.
Grendizer, Getter Robo G, Great Mazinger: Decisive Battle! The Great Sea Monster was produced by Dynamic Planning and Toei Animation and made in Japan. It was released on July 18, 1976.
- Director
- Masayuki Akehi
- Writers
- Susumu Takaku
- Release date
- July 18, 1976
- Original language
- Japanese
- Status
- Released
- Country
- Japan
- Production
- Dynamic Planning, Toei Animation
Grendizer, Getter Robo G, Great Mazinger: Decisive Battle! The Great Sea Monster cast & crew
Grendizer, Getter Robo G, Great Mazinger: Decisive Battle! The Great Sea Monster was directed by Masayuki Akehi and written by Susumu Takaku.
The cast features Akira Kamiya as Ryo Nagare, Hiroya Ishimaru as Kôji Kabuto, Keaton Yamada as Hayato Jin, Kei Tomiyama as Daisuke Umon / Duke Fleed, Keiichi Noda as Tetsuya Tsurugi, and Joji Yanami as Dr. Umon / Professor Yumi.
Behind the camera, it was produced by Chiaki Imada.
Is Grendizer, Getter Robo G, Great Mazinger: Decisive Battle! The Great Sea Monster worth watching?
At 0h 31m, it's an easy, time-light watch.
If you enjoy action, adventure, and animation, Grendizer, Getter Robo G, Great Mazinger: Decisive Battle! The Great Sea Monster is worth a place on your watchlist.
How and where to watch Grendizer, Getter Robo G, Great Mazinger: Decisive Battle! The Great Sea Monster
Grendizer, Getter Robo G, Great Mazinger: Decisive Battle! The Great Sea Monster isn't currently available on major streaming services in United States. We track availability continuously — add it to your watchlist and we'll keep an eye out.
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Cast of Grendizer, Getter Robo G, Great Mazinger: Decisive Battle! The Great Sea Monster

Akira Kamiya
Ryo Nagare

Hiroya Ishimaru
Kôji Kabuto

Keaton Yamada
Hayato Jin

Kei Tomiyama
Daisuke Umon / Duke Fleed

Keiichi Noda
Tetsuya Tsurugi

Joji Yanami
Dr. Umon / Professor Yumi

Rihoko Yoshida
Michiru Saotome

Hiroshi Otake
Boss

Kosei Tomita
Dr. Saotome
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Grendizer, Getter Robo G, Great Mazinger: Decisive Battle! The Great Sea Monster — FAQs
▸Where can I watch Grendizer, Getter Robo G, Great Mazinger: Decisive Battle! The Great Sea Monster in United States?
Grendizer, Getter Robo G, Great Mazinger: Decisive Battle! The Great Sea Monster is not currently available on major streaming services in United States. Availability changes often — check back soon.
▸What language is Grendizer, Getter Robo G, Great Mazinger: Decisive Battle! The Great Sea Monster in?
Grendizer, Getter Robo G, Great Mazinger: Decisive Battle! The Great Sea Monster is originally in Japanese. Subtitle and dub options vary by streaming service.
▸How long is Grendizer, Getter Robo G, Great Mazinger: Decisive Battle! The Great Sea Monster?
Grendizer, Getter Robo G, Great Mazinger: Decisive Battle! The Great Sea Monster runs 0 hours 31 minutes (31 minutes).



















