The Icarus affair (イカルス号事件, Ikarusu-gō jiken) was an incident involving the murder of two Royal Navy sailors in Nagasaki, Japan, in 1867, leading to increased diplomatic tensions between the United Kingdom and the Bakumatsu period Tokugawa shogunate.
[1][2] The British Consul in Nagasaki, Marcus Flowers, blamed the Tokugawa shogunate for failing to protect the men and believed that the Kaientai led by Sakamoto Ryōma was behind the killings.
[3] This belief was based on rumours that the men had been seen in the area, combined with the departure of Tosa steamers Yokobue and Wakamurasaki from Nagasaki soon after the incident.
Shōgun Tokugawa Yoshinobu was pressured by Sir Harry Parkes, head of the British Legation in Edo, to find the culprit.
There he was met by shogunate commissioners who had arrived earlier, to demand reparations from Tosa daimyō, Yamauchi Yōdō.