Kusaka was also the 4th Headmaster of Ittō Shōden Mutō-ryū Kenjutsu, a famous school of swordsmanship founded by Yamaoka Tesshū.

Born to a director of the Sumitomo zaibatsu in Tokyo in 1893, Kusaka's family registry officially listed him as a native of Ishikawa Prefecture, and he was schooled in Osaka.

His final assignment was command of the 5th Air Fleet after the suicide of Matome Ugaki, exactly the day Japan surrendered to the Allies.

Kusaka was interviewed by Walter Lord and gave detailed accounts for the books Day of Infamy (1957) and Incredible Victory (1967).

"Combined Fleet", released in the United States as The Imperial Navy) and by Ryûzô Hayashi in Toei's 2005 film Otokotachi no Yamato.