The Namamugi incident of September 14, 1862, is a political crisis mentioned by every history textbook in Japan. It occurred during the final years of the Tokugawa shogunate and changed the course of Japanese history thereafter, heralding the arrival of the modernization.

Shimazu Hisamitsu, the regent of the Satsuma Domain, was leading his retinue through the Namamugi village in Yokohama when he encountered four Britishers on horseback. According to the Japanese custom, commoners were supposed to make way for the lord, but the uninformed foreigners kept going through the parade, inciting the anger of Shimazu's bodyguards.

The samurai attacked the disrespectful British men, killing one (Charles Lenox Richardson) and injuring two others. While the Japanese regarded it as a justified act, the incident sparked outrage among Europeans for violating their extraterritoriality in Japan, and the Satsuma Domain's refusal to compensate for the damage resulted in the Bombardment of Kagoshima, known in Japan as the Anglo-Satsuma War.

The so-called "war" was fought for two days and caused the deaths of 63 British officers, while only one was killed on the Satsuma side. In its aftermath, Satsuma borrowed £25,000 from the shogunate to pay to the British, but never repaid as the shogunate fell in 1869 and was replaced by a new government. Richardson's killers were not identified nor put on trial, but the reparation was enough for Britain to sign a treaty with Satsuma.

The conflict actually helped Britain and Satsuma form a friendly relationship, with the Empire supplying the Domain with modern weaponry and warships. It is in no small part due to this that the samurai from Satsuma were the ones who contributed the most to the Tōbaku movement, a rebellion against the shogunate that ended the feudal period and westernized Japan.

Additionally, the British brought the Berkshire pig to Satsuma (present-day Kagoshima), where it continues to be a popular produce; in turn, Satsuma introduced Britain to a type of mandarin orange, which came to be known as the satsuma mandarin.

Today, the site of the murder that changed Japan is commemorated with a simple marker on a street in Yokohama, not much to see but a significant historic site. Also nearby, a memorial stele and the gravesite of Richardson in the Yokohama Foreign General Cemetery.