Mutsu Munemitsu
Kōno was born in Kōchi, Tosa Province (present-day Kōchi Prefecture) as the eldest son of a local low-ranking "samurai". He was sent to Edo in 1858 where (along with Mutsu Munemitsu) he studied under the noted Confucian scholar, Yasui Sokken. On his return to Tosa in 1861, he joined the movement organized by Takechi Hanpeita and Sakamoto Ryōma and became active in the "Sonnō jōi" movement. In 1862, along with 59 other Tosa samurai, he marched on Kyoto and Edo in an attempt to influence national policy, but was captured by security forces of the Tokugawa shogunate in 1863 and sentenced to six years in prison. Tortured while in prison, he refused to recant and his sentence was extended to life imprisonment.