- Born: 1802
- Died: 1850
- Other Names: 亀松 (childhood name: Kamematsu); 夢酔 (retirement name: Musui)
- Japanese: 勝小吉 (Katsu Kokichi)
Kokichi was born Kamematsu, the third son of Otani Heizô, who in turn had been the third son of a wealthy moneylender before being adopted into the Otani clan. The Otani were a low-ranking family with a stipend of 100 koku. Kokichi's eldest half-brother, Otani Hikoshirô, became head of the Otani family after their father's retirement. Hikoshirô is known as a Confucian scholar, calligrapher, and district administrator. Kokichi's other half-brother, Otani Saburôemon, was adopted into the Matsusaka family, and also served as a district administrator. Their father, Otani Heizô, died in 1827 (when Kokichi was 25).
Not being the eldest son, and thus not likely to become the next head of the Otani family, Kamematsu was adopted into the Katsu family in 1808, at age seven, and given the name Kokichi. Though he was only seven, he was claimed to be seventeen, and the pate of his head shaved as if he had had his coming-of-age ceremony (genpuku); this was done because shogunate law mandated that one could not be formally adopted before age seventeen. Kokichi would later marry the family's only daughter, Nobuko, and thus become the head of the Katsu family. Her parents had passed away prior to Kokichi's adoption, and so he and his wife-to-be were raised by her grandmother.
Kokichi began attending school at the Yushima seidô in 1813, but only very briefly, as he did not devote himself to his studies, and was soon removed from the school; he had already been practicing horseback riding and martial arts for a number of years, however, and excelled at these.
Kokichi married Nobuko when he was seventeen; the two of them, along with her grandmother, then moved into a house on the grounds of his brother's Hikoshirô's home.
Kokichi had four children with Nobuko - a son named Rintarô (who would come to be known as Katsu Kaishû and as "father of the (modern) Japanese navy"), and three daughters.
The Katsu family had declined dramatically in its fortunes during the time when Nobuko's father was head of the family, to the point where the family's stipend was a mere 41 koku, though the reputation associated with the family name still held some value. Kokichi spent many of his early years seeking formal government employment through the kobushingumi system, but after his father's death in 1827, he gave up on the effort.
He passed on the headship of the family to his 15-year-old unmarried son Rintarô in 1838, and took the name "Musui," meaning, roughly, "drunk on dreams," as his name in retirement. Despite having lived most of his life largely illiterate, in 1843 he wrote the autobiography Musui dokugen (lit. "Musui talking to himself"), which was in 1988 translated into English by Teruko Craig and published.
- Craig, Teruko (trans.). Musui's Story: The Autobiography of a Tokugawa Samurai. University of Arizona Press, 1988.
- By traditional Japanese age calculation; six by Western reckoning.