What magazine did Attack on Titan run in?
Bessatsu Shōnen Magazine (“Bessatsu” means a special or extra issue) is Kodansha’s monthly companion to Weekly Shōnen Magazine. It launched in 2009, and Attack on Titan was a headline title of its first issue, the October 2009 issue released on 9 September 2009. The final chapter ran in the May 2021 issue, released 9 April 2021: the series and the magazine grew up together, cover by cover, for eleven and a half years.
The monthly rhythm shaped the book. Where a weekly series burns four short chapters a month, Isayama delivered one long chapter (around 45 pages) per issue, which is why the 34 volumes hold four or five chapters each and read in arcs rather than episodes. Bessatsu also carried most of the family: Junior High and the Lost Girls manga both serialized there, while Before the Fall ran in Monthly Shōnen Sirius and No Regrets in the shōjo magazine Aria.