The purpose of the study was to identify HORI Kosai and the student organization, “Bijutsuka Kyoto Kaigi” (in short, Bikyoto, which means Artists Co-Struggle Council in English), which he initiated; this study also evaluates the important role he played as an artist at the end of avant-garde, and during the instability of the late 60’s student movement. There are three main points to this study. Firstly, to point out the crisis at the end of avant-garde, and through reviewing Bikyoto, we identified HORI’s artistic motive. Secondly, to discuss HORI’s earlier exploration in multiple genres, as well as his experience in Bikyoto, and bring a focus to what shaped his art practice prior to 1980. Thirdly, I’d like to emphasize how HORI’s paintings and performances after 1980 extend the thoughts and ideas of Bikyoto. In conclusion, this study is to examine how HORI used the Bikyoto ideas to explore and progress his art practice, as well as how his performances weren’t merely an extension of his paintings’ boundary, both of which are independent entities, but mutually influenced each other.