During World War II, Dr. Asagumo is brought to Nazi Germany, where Hitler personally requests his cooperation in researching the new weapon "Big X." Worried about the consequences should Big X be completed, Dr. Asagumo deliberately slows the research's progress while secretly working alongside his fellow researcher, the cunning Dr. Engel. Just before Germany falls to the Allied forces, Dr. Asagumo plants a card inscribed with Big X's secret inside his son Shigeru, and is then fatally shot by the German military. Twenty years later, the card is found within Shigeru, who now resides in Tokyo. Shortly afterward, an organization claiming ties to the Nazis appears, steals the card, and brings the Big X project to completion. Dr. Engel's grandson has thrown in his lot with the Nazi Alliance. The finished Big X proves to be a drug capable of enlarging the human body without any limits. After reclaiming Big X from the enemy, Shigeru's son Akira boldly takes on the Nazi Alliance and Hans Engel, who scheme to dominate the world.
Note: Most of the series is lost media. Only episodes 1, 11, 12 & 40-59 are known to still exist.
