It was the box-office weekend that rocked the world.

"Demon Slayer: Kimetsu no Yaiba the Movie — Mugen Train" opened in Japan on Friday, Oct. 16. By the following Monday, it had pulled in around ¥4.6 billion (almost $44 million), the best opening in Japanese box-office history. As the dust settled, industry watchers worldwide were asking themselves two questions: How did a film make that much money in the middle of a pandemic? And, what the heck is "Demon Slayer"?

The popularity of the latter helps explain the former. The film is based on the manga "Demon Slayer: Kimetsu no Yaiba," which is set in Japan's Taisho Era (1912-26) and revolves around a young man's quest to restore the humanity of his sister, who has been turned into a demon that craves human flesh. As the title suggests, he also does some demon slaying along the way.