Otoya Yamaguchi (山口 二矢, Yamaguchi Otoya; 22 February 1943 – 2 November 1960) was a Japanese radical anti-communist and ultranationalist youth who assassinated Inejirō Asanuma, chairman of the Japan Socialist Party, on 12 October 1960.
Yamaguchi rushed the stage and stabbed Asanuma with a wakizashi-like short sword while Asanuma was participating in a televised election debate at Hibiya Public Hall in Tokyo. Yamaguchi, who was 17 years of age at the time, had been a member of Bin Akao's far-right Greater Japan Patriotic Party, but had resigned earlier that year, just prior to the assassination. After being arrested and interrogated, Yamaguchi committed suicide while in a detention facility.
Yamaguchi became a hero and a martyr to Japanese far-right groups, who as of 2022, have continued to hold commemorations to this day. Yamaguchi's actions inspired a number of copycat crimes, including the Shimanaka incident in 1961, and inspired Nobel Prize-winning novelist Kenzaburō Ōe's novellas Seventeen and Death of a Political Youth. A photograph of the assassination taken by Japanese photojournalist Yasushi Nagao won World Press Photo of the Year for 1960 and the 1961 Pulitzer Prize.
Yamaguchi was born on 22 February 1943 in Yanaka, Taitō, Tokyo. He was the second son of Shinpei Yamaguchi, who by 1960 would become a high-ranking officer in the Japan Ground Self-Defense Force, and was the maternal grandson of the famous writer Namiroku Murakami, well known for his violent novels glorifying the chivalric code of Japanese organized crime syndicates known as the yakuza.
Yamaguchi began reading newspapers starting in his early childhood. Angered by what he read, he became interested in nationalist movements and vehemently critical of politicians. Due to his father's job changes and transfers, Yamaguchi had to move frequently during his childhood, transferring between two elementary schools, three middle schools, and two high schools. As a result, he grew up with few close friends. He lived in Sapporo, Hokkaido for much of his childhood because of his father's work. In 1958, he was accepted into Tamagawa High School in Tokyo, however his father transferred him to Sapporo Kōsei, a local Catholic school in Sapporo. Yamaguchi then decided to move to Tokyo to live with his brother, and transferred back to Tamagawa High School.
Yamaguchi exhibited intense xenophobia from childhood, harboring deep revulsion toward foreigners, particularly Koreans and Chinese whom he perceived as "domineering" over Japan, fueling his early nationalist resentments.
He also developed profound hatred for left-wing groups, including communists, socialists, and labor unions (such as Nikkyoso), associating them with post-war incidents like the Mitaka, Shimoyama, Shiratori, and Matsukawa cases, which he viewed as existential threats to Japan's national integrity.
Described as contrarian and rebellious from a young age, often arguing the opposite of others (for example: insisting "left" if someone said "right"), Yamaguchi frequently clashed with teachers over ideological differences and felt alienated in school environments, contributing to frequent school transfers and general isolation. He was portrayed as a lonely youth who ignored parental and school advice, ultimately dropping out of high school to dedicate himself fully to extremist activities. Through the influence of his brother, he began attending speeches and participating in protests and counter-protests organized by various right-wing groups.
On 10 May 1959, at age 16, he heard a speech by right-wing ultranationalist Bin Akao declaring that Japan was on the verge of a revolution, and that the youth must begin resisting the actions of left-wing groups. This speech had a profound impact on him. After the speech, while Akao was planning to go to the next location, Yamaguchi told Akao that he wanted to go along with him, but Akao gently declined. Following this, he formally joined Akao's Greater Japan Patriotic Party.
Akao was virulently anti-communist and strongly pro-United States. Thus when left-wing protesters, led by Asanuma and the Japan Socialist Party, staged the massive Anpo protests against the 1960 revision of the U.S.-Japan Security Treaty (known as "Anpo" in Japanese), Akao became convinced that Japan was on the verge of a communist revolution and mobilized his followers to stage counter-protests. Yamaguchi participated in these counter-protest activities, and was arrested and released 10 times over the course of 1959 and 1960, within his first six months since joining Akao's party.
Yamaguchi's involvement with the Greater Japan Patriotic Party involved aggressive anti-communist actions, including disrupting left-wing events with propaganda, which led to repeated arrests (at least 10–17 documented incidents in 1959–1960) for offenses such as assault (throwing glue at opponents, striking individuals), obstruction of public duties, property damage, violence, and power abuse.
Examples include driving propaganda vehicles into venues (causing injuries), physical clashes with leftists and police during Anpo protests, and repeated violations despite parental and party leader warnings to curb aggression.
Due to this chronic pattern of violence, he was placed under four years of protective observation, indicating a disregard for legal consequences.
Over the course of his participation in the Anpo protests, Yamaguchi became further disillusioned with Akao's leadership, which he felt was not radical enough. In his testimony to the police after the assassination of Asanuma, Yamaguchi stated that Akao was always talking about taking out left-wing leaders, but was only interested in protests and media coverage, and that Akao would stop him if he ever tried to act on his words. Later in the interview, he stated that he had resigned from Akao's party in order to "lay [his] hands on a weapon" and be free to take more "decisive action".
Akao, who had known Asanuma since their time on Miyake-jima, described him as “a good person, which makes it regrettable to deal with him” (善人だから始末に悪い), a comment some sources suggest influenced Yamaguchi’s motives alongside Asanuma’s statement labeling American imperialism as the common enemy of Japan and China, as recorded in Yamaguchi’s Memorial of Severing the Traitor. Despite this recognition of Asanuma’s personal character, Akao later celebrated Yamaguchi’s act.
Alongside Akao's influence, Yamaguchi was also inspired by the doctrine of the religious movement Seichō no Ie, particularly through founder Masaharu Taniguchi's writings such as Tennō Zettai-ron to Sono Eikyō (Absolute Theory of the Emperor and Its Influence), which Yamaguchi credited in his interrogation records with helping him overcome personal hesitation and embrace selfless loyalty to commit the act, Asanuma himself supported the founder of this movement, Masaharu Taniguchi. Taniguchi affirmed that Seichō no Ie was neither opposed to the Socialist Party nor aligned with the Liberal Democratic Party.
On 17 June 1960, when a right-wing youth attacked Jōtarō Kawakami, a Christian socialist and an adviser to the Japan Socialist Party, he commented:
On 1 July, together with his comrades, he took part in the establishment of the Tokyo Branch of the All-Asia Anti-Communist League.