Dr. Juzou Oki heads the Oki Ocean Lab and designed the experimental submarine SS-99, naming it after the family's Type-99 rifle. His pioneering L-type engine powers the vessel without radiation emissions, enabling flight through its phase 2 engine and eventual space travel after post-war modifications.

He investigates oceanic threats aboard the survey submarine Kuroshio, launched from the Kairyumaru. During this mission in the Japanese Trench, the Ocean Empire attacks, and he vanishes after entrusting his grandson Susumu with a key marked "SS-99."

Captured by the Ocean Empire, Dr. Oki is forced to develop military technology for commander Hell Deathbird, including the Z-type aircraft-carrying submarine. His expertise becomes vital to the empire's operations during this period.

As patriarch of the Oki family, his son Goro serves as deputy officer at the lab and accompanies him on the Kuroshio expedition. Susumu later becomes chief mechanic of the SS-99.

Dr. Oki's legacy extends beyond the SS-99's combat role. Thirty years after the conflict, the submarine is upgraded for space exploration, reflecting his designs' enduring impact. The anime's final epilogue shows a spacefaring SS-99 crewed by figures resembling Susumu and Miyuki Moriki.

His work becomes humanity's primary defense against oceanic domination.