Kusunose was born as the eldest son to a samurai family of the Tosa Domain (present day Kōchi Prefecture).

He entered the Imperial Japanese Army in December 1880, serving in artillery, and was sent as a military attaché for training in France and Prussia from 1881-1885.

Kusunose was posted as a resident officer to the Japanese embassy in Saint Petersburg, Russia, from April 1891 to September 1893, and came to be regarded as a leading expert on European affairs.

Kusunose was present in Seoul during the assassination of Queen Min and on his return to Japan he was arrested (along with Miura Gorō and several other civilian and military members of the Japanese consulate).

Along with Miura, Kusunose was released after a military tribunal by the IJA 5th Division found them innocent due to "lack of evidence.