Satou explains that in early 2000 the media started a public manhunt for Tanaka, most likely leading to his capture and rumors of a reward for an Ajin's discovery. (Ch 13.)
So Tanaka probably spent about a decade, give or take a few months(?), getting treated as a labrat.
Also Satou's backstory flashback indicates that he enlisted in the army in 1969, lying about his age. Assuming he was 16 or 17 pretending to be 18, he'd be either 58 or 59 during the manga's main timeline. (?!)
no subject
Main story takes place starting in July. Nagai Kei is discovered as an Ajin shortly after July 23rd. (Ch 1.) Given the dates and matching days of the week, the year is probably 2011. (Ch 31.)
Satou explains that in early 2000 the media started a public manhunt for Tanaka, most likely leading to his capture and rumors of a reward for an Ajin's discovery. (Ch 13.)
Satou is shown looking at images of Tanaka's torture on June 16. (Ch 3.) In the present-day timeline (July 23, 2011 onwards), Tosaki says that "the attack on Subject 002's experimental facility took place one month ago". (Ch 5.) Satou probably broke Tanaka out of the facility sometime in mid-to-late-June, 2011.
So Tanaka probably spent about a decade, give or take a few months(?), getting treated as a labrat.
Also Satou's backstory flashback indicates that he enlisted in the army in 1969, lying about his age. Assuming he was 16 or 17 pretending to be 18, he'd be either 58 or 59 during the manga's main timeline. (?!)
Maybe Ajin age slower?