Ishimoto came to Finland from Japan in 1970 and has lived there ever since. He first worked for the company Decembre, set up by Ristomatti Ratia, son of Marimekko's founders Armi and Viljo Ratia. Ishimoto switched over to Marimekko in 1974.
His highly personal style gave Marimekko a boost during the 1970s and 1980s with more mature and abstract designs than the playful 1960s styles which first had made Marimekko famous. Inspired by traditional Asian art and culture but also by Finnish traditions and nature, Ishimoto has continued to reinvent himself.
In total, he has made over 300 designs for Marimekko. Besides his work for Marimekko, he also creates unique ceramic works and was recently the subject of a large retrospective exhibition in Helsinki.