Hiroyasu Koga (Japanese: 古賀浩靖 Koga Hiroyasu, born 15 August 1947) is a former Tatenokai member and kaishakunin responsible for the decapitations of Yukio Mishima and Masakatsu Morita during their seppuku on November 25, 1970.
Koga, known by the nickname Furu-Koga (distinguishing him from another Tatenokai member named Masayoshi Koga who was in turn nicknamed Chibi-Koga, 小賀), was a skilled practitioner of kendo (swordsmanship).
[1] Koga and two other participating Tatenokai members (Masayoshi Koga and Masahiro Ogawa) went on trial on March 24, 1971,[2] facing charges of bodily injury, violence, illegal possession of firearms and swords,[3] and assisting a suicide.
[4] They were convicted and sentenced to four years' penal servitude, and were released in 1974, a few months early.
[6] However, an alternative belief is that he never became a Shinto priest, instead becoming the head of the Hokkaido branch of Seicho no Ie and was renamed Hiroyasu Arechi.