Ichimura started in aikido in 1955, at Aikikai Hombu dojo in Tokyo with Shoji Nishio as his main teacher. In 1961 he went to the Toyo University, where he started a university dojo in which he self taught. In 1966 he moved to Stockholm in Sweden, since Jan Beime and a few other people had asked Hombu to send an aikido teacher there. To start with Ichimura was based in Beime's dojo, Stockholm Aikikai, and later at Minnano. He also travelled, teaching in many different dojos in the Stockholm area. In 1968 he moved to Uppsala, roughly 70 kilometres north of Stockholm, where he started a new dojo in cooperation with the local YMCA. The dojo has since changed name, and is nowadays often referred to as Uppsala Aikikai. In the years to come Ichimura taught in Uppsala as well as in Stockholm and other places in Sweden, and also taught seminars in Finland, Denmark and Poland.
Ichimura was known as an inspiring teacher, but also many conflicts arouse around him. Among the traces he left in Swedish aikido are a connection between aikido and iaido; most of the older aikido practitioners in the country have done also iaido. The part of Scandinavian aikido who do Nishio's type of aikido originally had this connection from Ichimura. Ichimura also wrote two of the first aikido books in Swedish, Aikido and Aikido och fred (literally "Aikido and peace").
In 1986, Ichimura returned to Japan, leaving Sweden without a Japanese teacher in charge while Yasuo Kobayashi took responsibility for Finland, and Nishio for Denmark. Ichimura no longer does aikido, but has a shiatsu clinic in Kobe (early 2000s).