After graduating from Gunma Prefectural Maebashi Commercial High School in 1969, Adachi worked as an assistant for Isami Ishii.
Adachi is well known for romantic comedy and sports manga (especially baseball) such as Touch, H2, Slow Step, Miyuki and Cross Game.
He has been described as a writer of "delightful dialogue", a genius at portraying everyday life,[2] "the greatest pure storyteller",[3] and "a master manga artist".
In addition, it has been suggested that the accurate portrayal of sibling rivalry in Touch may come from Adachi's experiences while growing up with his older brother.
In 1969, he followed his older brother's lead and moved to Tokyo to begin work as an assistant to manga artist Isami Ishii.
Adachi then released Niji Iro Tōgarashi, a fantasy medieval romantic comedy manga series, from 1990 to 1992 in Weekly Shōnen Sunday.
Due to achieving total manga sales numbering over 200 million volumes, Weekly Shōnen Sunday devoted issue 26 in 2008 to Adachi and his works.
Asaoka High School Baseball Club Diary: Over Fence began in the April 27, 2011, issue of Weekly Shōnen Sunday.
[7] In May 2012 he finished Q and A and began his new series, Mix, a semi-sequel to Touch set 30 years later, in the June 2012 issue of Monthly Shōnen Sunday.