Itosato (date of birth and death unknown) was a woman who lived during the end of the Edo period. In the part of an assassination of Kamo SERIZAWA stated in "Roshi (masterless samurai) Bunkyu Era Patriotism Articles" and "Shinsengumi Tenmatsuki"that were written by Shinpachi NAGAKURA of Shinsengumi, she appeared as 'Wachigaiya Itosato' who was present when the incident occurred.
Wachigaiya was an okiya (geisha dwelling) of Kyoto Shimabara, and she was a Tenjin; an upper rank prostitute (geisya). Jusuke HIRAMA, Fukucho jokin (assistant vice commander) of the Shinsengumi in the early years used to regularly see her. HIRAMA was from Mito province and belonged to the group of Kamo SERIZAWA, the head of the group. "Shinsengumi Ibun" (Curious stories about Shinsengumi) that were written based on the stories heard from Tamesaburo YAGI (the son of Yagi family in which Shinsengumi quartered) by Kan SHIMOZAWA in the early Showa period described how Itosato acted on the day of the incident.
On September 18 in 1863, Tamesaburo and his younger brother went to a bed room which was located on the left side of the entrance after sunset, they saw an unfamiliar woman crouched on the floor. Tamesaburo and his younger brother were frightened to see her, and let their mother know about it. She didn't seem surprised at all, and laid a mattress in the other room. Since Roshi-gumi (an organization of masterless samurai) quartered in their place, a samurai often entered in their house with his close girl friend without saying anything. This woman was Itosato.
After that, Goro HIRAYAMA's geisya girl friend, Kichiei KIKYOYA came, and she talked and laughed in the kitchen with a maid of Yagi family and SERIZAWA's girl friend, Oume.
After a while, SERZAWA, HIRAYAMA, and HIRAMA came home, and SERIZAWA and Oume, HIRAYAMA and Kichiei, entered into the 10 tatami mat bed room at the back of the house to go to sleep while HIRAMA entered into the bed room next to the entrance where Itosato was to go to sleep.
When they fell into a sleep late at night, suddenly a few men (probably they were Toshizo HIJIKATA, Keisuke YAMANAMI, Soji OKITA, Sanosuke HARADA from Shieikanha group) stepped in the bed room at the back; they killed SERIZAWA and HIRAYAMA, as well as Oume who was present at that moment.
HIRAMA was amazed and rushed around the house when he heard a sound, then he ran away from the house as he sensed the situation. When Isami KONDO and Toshizo HIJIKATA (they were the main players of the assassination) came to the Yagi house for questioning the situation, Itosato and Kichiei were gone.
There was no record of Itosato in Wachigaiya, and her past and what happened to her after the assassination were completely unknown.
In the Showa period, Shimabara became deserted, and almost every Okiya or ochaya (literally "teahouse" which refers to places where geisha entertain their guests) closed a business; Wachigaya still continues their business until now, and its building is designated as Kyoto Culture Foundation.
In 2004, Jiro ASADA wrote "Wakachiga Itosato", a period novel, in which Itosato was a main character. As mentioned above, nothing was known about Itosato, apart from the fact she was present when Kamo SERIZAWA was assassinated; her character in the story was all fictional.