KANAI together with Hirondo TOMIZU, Masaakira TOMII, Toru TERAO, Sakue TAKAHASHI, Kiheiji ONOZUKA, and Shingo NAKAMURA submitted the opinion in writing (The Written Opinion of Seven Scholars) supporting the pro-war position and swayed the public opinion in the direction of opening the war in June, 1903 preceding the Russo-Japanese War.
日露戦争に先立つ1903年6月、戸水寛人、富井政章、寺尾亨、高橋作衛、小野塚喜平次、中村進午らと共に開戦論を主張する意見書（七博士意見書）を提出し、世論を開戦の方向へと位置付けた。