Manga written and drawn by Tatsuya Endou, SPY x FAMILY, surpassed 5,500,000 circulating copies including volumes’ 5 initial print.
Synopsis, according to official MANGA Plus website, is as follows:
The master spy codenamed <Twilight> has spent his days on undercover missions, all for the dream of a better world. But one day, he receives a particularly difficult new order from command. For his mission, he must form a temporary family and start a new life?! A Spy/Action/Comedy about a one-of-a-kind family!
The series was reported to have passed 4 million copies just a little less than 2 months ago, and Volumes 1 to 4 each have over 1 million (electronic versions included). The initial print of Volume 5 is also included.
With each copy of the 5th volume of SPY x FAMILY, readers will also receive a small dress-up stand of Aya as a bonus. The stand is drawn by the author of the manga himself.
Source: Official twitter account of the editor of the manga