Hajime Isayama's hit action-fantasy manga "Attack on Titan" has more than 60 million copies in print, Kodansha's Bessatsu Shōnen Magazine announced this week.

Anime News Network notes the manga had surpassed 52 million copies as of October 2015. The 20th collected volume was released last month in Japan.

Debuting in 2009, "Attack on Titan" depicts the battle between the last remnants of humanity who live in cities surrounded by enormous walls and the flesh-eating giants who roam the outside world. The series initially centers on Eren Yeager, his adopted sister Mikasa Ackerman and their childhood friend Armin Arlert, who join the military after the town is invaded by Titans and Eren's mother is eaten. The story later shifts to focus on other characters as the truth about the Titans is revealed.

The manga has inspired a blockbuster anime series, which will return next year for a long-awaited second season, a two-part live-action film and a live-action television spinoff. That's in addition to spinoff manga like "Attack on Titan: Junior High" and "Attack on Titan: No Regrets," which also received anime adaptations, and novels and video games.

"Attack on Titan" is published in English by Kodansha Comics, which released the 19th volume Aug. 2 in North America.