A signboard (seisatsu) proclaiming that Chôshû han was an enemy of the Imperial court, was placed near the Sanjô bridge.
On 1866/8/28, the seisatsu was pulled down and trashed on the side of Kamo River. On 9/2, the seisatsu was replaced, however it was gone again in three days.
On 9/10, the bakufu replaced the seisatsu again and ordered the Shinsengumi to keep watching it, knowing that Chôshû loyalists were responsible, and would likely return.
The Shinsengumi sent 34 members in three groups:
- Ôishi Kuwajirô's unit-10
- Arai Tadao's unit-12
- Harada Sanosuke's unit-12
Hashimoto Kaisuke and Asano Kaoru dressed like beggars and sat on the side of Sanjô Bridge in wait.
At midnight of 9/12, eight Tosa han samurai showed up and pulled the seisatsu down. Arai's unit and Harada's unit killed or captured three of them, but they missed five others.
Ôishi's unit was late because Asano, who was supposed to let them know if anyone showed up, was scared of the Chôshû samurai and took the long way to the place where Ôishi's unit was located.
References
- Shinsengumi 100 Wa (新選組100話) Suzuki Toru