In July 1643, the Yoshinaga Domain was founded; Akitomo's father, Akinari KATO, who was the lord of the Aizu Domain, had his domain with 400,000 koku of rice confiscated in June 1643, but continuance of the family name was allowed because of the deed of valor of Akitomo's grandfather, Akinari KATO.
寛永20年（1643年）5月、父・加藤明成が会津藩40万石を収公されたが、祖父・嘉明の勲功により家名存続を許され、6月に立藩した。