Before Shiro and Tobei can head out to Shikoku to the hotel she works in, they fall under attack by cannon shells and Professor Okita is mortally injured in one of the blasts. Professor Okita explains his situation to Shiro and Tobei and that his sister has the map to the location of the Satanium vein. Enraged, Shiro transforms into V3 and pummels the kaijin forces while Destron tries to take Professor Okita away with them, but V3 rescues him and escapes before the island explodes. Shiro fights several Combatmen and then several revived Destron kaijin who inform Shiro that the prisoners are all dead. Doctor G orders the prisoners to quickly be killed and to abandon the island base, rigging it to self destruct. The Great Leader inquires to Doctor G if Professor Okita has revealed to them the location of the mineral deposits, but the latter says that the professor will not talk but he soon will.Ī Destron Combatman sounds the alarm that they have an intruder that has broken in, revealing Shiro is inside. Doctor G is pleased with the results, desiring more of the mineral so that Destron can rule the world. The other subjects are also brutally killed by the Satanium’s radiation and it is then placed back in its containment room. One prisoner is exposed to extremely high levels of radiation, his cells grow tumors and then his body melts away, leaving a dead skeleton on the floor. The test puts the Satanium in a room with three prisoners as guinea pigs.

Professor Okita tries to stop them but is restrained and put in a cell. In the base, Doctor G orders his Destron Scientists to begin testing the Satanium. Shiro sneaks his way towards the island by scuba diving while Tobei move his boat away from sight. They then find a small island with Destron Combatmen on guard, giving away the location of Destron’s latest hidden base. Upon heading there to investigate, Tobei and Shiro disguise themselves as fishermen on the water and observe the islands for possible clues. Shiro arrives and Junko receives radio transmissions from the Maritime Safety Agency about their search for the professor, Okita’s jacket was found off the coast of Katsura in Kyoto. Tobei Tachibana reads the paper, with the headline being the disappearance of Professor Tetsuo Okita. The agent then kidnaps Professor Okita to learn the location of the Satanium mineral deposit so Destron can conquer the world with the element.

His thoughts are interrupted by an agent of Destron, who stalks Okita and stops him when he tries to throw the isotope overboard to get rid of it. The professor is so concerned about what a dangerous element Satanium is that he considers abandoning his research. In a flashback, Okita used a giger counter in the mountains to survey the area and collect a sample for study. Professor Okita is concerned about how dangerous the element is if a large quantity is collected. The film opens on a cruise ship called The Sunflower carrying atomic physics professor Tetsuo Okita, who had discovered a new isotope element called Satanium in the Shikoku mountains, an element several hundreds of times more powerful and radioactive than uranium. Kamen Rider V3 must act fast in rescuing Professor Okita and preventing Destron from collecting more of the deadly mineral. However, Destron abducts Okita in hopes of finding the source of Satanium and collecting more of it to expedite their run for global domination. A physicist named Tetsuo Okita discovers a new mineral called ' Satanium,' which is more powerful than uranium and emits destructive effects to anyone exposed to it.

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