A father hides a weapon's secret inside his own son's body, then dies before he can explain why. Fifty-nine episodes later, you're watching a kid run from Nazi remnants, Soviet spies, and his own father's ghost, all hunting the one thing implanted in his chest. This is pulp sci-fi from an era when anime could be utterly unhinged without irony, where the plot keeps escalating because nobody told the writers to stop.

A scientist's deadly secret carries forward two decades after World War II ends. Dr. Asagumo spent the war quietly stalling Hitler's Big X weapon project, then hid its secret on a card implanted in his own son, Shigeru, shortly before German soldiers killed him. Twenty years later the card is found inside Shigeru in Tokyo, and a group claiming ties to the Nazis steals it and finishes the project. Big X turns out to be a drug that lets the human body grow without limit. Shigeru's son Akira gets hold of Big X and boldly fights the Nazi Alliance and Hans Engel, grandson of Asagumo's scheming former colleague, who aim to conquer the world. The show is a 1964 action and science fiction TV series, and most of its 59 episodes are now lost.