Big X is a science fiction manga series and an anime series by Osamu Tezuka, based on actual experiments conducted by the Nazis to create secret weapons toward the end of World War II.
Invited to Nazi Germany during World War II, Dr. Asagumo is asked by Hitler to collaborate in researching the new weapon “Big X”. Concerned about the possible effects this weapon, Dr. Asagumo intentionally delays the progress of the research, conspiring with his co-researcher, the devious Dr. Engel.
Immediately before Germany is defeated by the Allies, Dr. Asagumo, before being shot to death by the German army, implants a card inscribed with the secret of Big X into his son, Shigeru.
Twenty years later the card is discovered; an organization claiming alliance with the Nazis appears, steals the card from Shigeru, who now lives in Tokyo, and completes the Big X project, which is revealed to be a drug that can expand the human body without limitation. Along the way it is discovered that Dr. Engel’s grandson has joined the Nazi Alliance. Recovering Big X from the enemy, Shigeru’s son Akira fearlessly challenges the Nazi Alliance and Hans Engel, who are plotting to conquer the world.