He studied swordsmanship under Takechi Hanpeita Zuizan. Yoshimura admired the sonnô jôi ("revere the emperor, expel the barbarians") ideology, and joined the Tosa Loyalist Party which Takechi helped found. He interacted with Kusaka Genzui, Hirano Kuniomi, and others, and was influenced by the "revere the emperor, topple the shogunate" ideology.
In 1862, when Sakamoto Ryôma and others left the han and journeyed to Kyoto, becoming active in national affairs, Yoshimura accompanied them, but was arrested in the Teradaya Affair, sent back to Tosa, and imprisoned. After being released on bail, he returned to Kyoto and established a temporary residence for himself in Kiyamachi, next door to Takechi's residence "Funatora."
The following year (1863), along with Chamberlain Nakayama Tadamitsu (the uncle of Emperor Meiji) and others, he helped form the Tenchûgumi. They raised an anti-shogunate army in Yamato province, and occupied the offices of the Gojô Daikan (Gojô Magistrate). There was a change in government, however, on 8/18, and thus a change in the situation, and their army met shogunate forces in battle. Yoshimura was killed in battle on 9/27 at Yoshino in Yamato province.
- Plaques on-site at Yoshimura's former residence in Kyoto Kiyamachi.