Two innocent men are hiking along when there is an earthquake. That's not unusual, so they just keep on going. However, pretty soon they see red mist pouring out of a cave in the hillside. Curious (the fools!), they enter the cave. They find some artifacts, two bizarre carvings on the wall. Backing up, they knock over a vase, which shatters. Out of it forms a huge, toothy monster that kills them. It then goes into Tokyo, seeking human champions. It faces and kills a boxer, then a samurai. Despairing of finding an appropriate champion, it is hurrying across Tokyo when it stumbles upon Radiege and the Jetmen fighting in a park. It makes a general attack on them. Kaori manages to get in a hit that takes off one of its arms. It regrows the arm immediately and stuns Radiege and the Jetmen. It snatches up Kaori and takes her unconscious self with as it races back to the cave. Immensely curious, Radiege follows.
The creature's name is Muu. It is the servant of two ancient gods, Majin Ramon and Majin Googu of the Taiko era (I have no idea). These lovely beings (eeeesh) have slept in this cave for a LOOOONG time, waiting for Muu to free them by bringing them blood sacrifice. Whether Muu's goal to search for a powerful champion as sacrifice was his own or their idea, wasn't really covered.
Gai arrives in time to see Kaori placed in the sacrificial humanoid-shaped indent in the wall, and tentacles spring from the stone gods towards her. She screams. He pulls out a knife and slices open his palm. The fresh blood scent brings the tentacles after him. He endures the draining of his blood. Kaori, seeing him thus, remembers all the times he's put his life on the line for her, and realizes that she does indeed love him. She tells him so but he is weakening and can only smile in response. The other Jetmen arrive and blast him loose, taking both of them from the cave.
Mu is in a panic. He goes out to fight the Jetmen. Meanwhile, Radiege steps into the cave. He offers his own blood to the stone gods and lets them drain him. They wake from their long sleep and take flesh. Muu comes, but he is injured mortally, and so they kill him. The chamber begins to quake and break apart. Ramon and Googu leave, ignoring Radiege. Furious, he pursues them.
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