[1] Shirai held the title of Shihan and was responsible for taking the dan examinations within SCI and, together with Carlo Fugazza, for those within the FIKTA.

After a world trip to promote karate together with Taiji Kase, Hirokazu Kanazawa, and Keinosuke Enoeda to Europe, South Africa, and the United States of America, he settled in Milan, Italy in 1965.

[5] Shirai felt that the self-defence (goshindo) aspect of Shotokan karate has been too much in the shadow of kumite and kata.

Although he practised karate for self-defence initially, he focussed on kumite for a few years until moving to Europe.

[4] During his last years Shirai gave special goshindo oriented stages in Europe, often together with Claudio Ceruti, Massimo Abate, and Angelo Torre.