Pluton no Musukotachi
プルトンの息子たち
Rieko, the granddaughter of scientist Eisaku Shirakawa, visits the Yamato, a drilling probe where her brother Ryuu is working. Shirakawa had been involved in a Nazi-sponsored secret project during World War II related to the Hollow Earth theory. While the Yamato is docked, it unexpectedly begins drilling uncontrollably, leaving Ryuu and his colleague unable to stop it. The intense heat causes the three to collapse. Upon waking, they realize they have reached the interior of the Earth.