During a televised debate, 17-year-old right-wing ultranationalist Otoya Yamaguchi charged onto the stage and fatally stabbed Asanuma with a wakizashi, a type of traditional short sword.

The massive left-wing protests made Akao, his party and many other right-wing groups convinced that Japan was on the verge of a communist revolution.

Akao gave numerous public speeches, of note mentioning the importance of the youth's role in resisting their political rivals.

[12] In his testimony given to police, he stated that he resigned from Akao's party in order to "lay [his] hands on a weapon" and be free to take more "decisive action.

"[12] On October 12, 1960, Asanuma was participating in a televised election debate at Hibiya Public Hall in central Tokyo, featuring the leaders of the three major political parties.

Immediately, right-wing groups in the audience began loudly heckling him, and the television microphones and reporters sitting in the front row could not hear him, forcing the NHK moderator to interrupt and call for calm.

Ikeda's newly announced Income Doubling Plan had proven popular, and polls showed his party in a strong position heading toward the election.

Within a few weeks of the assassination, Nobel Prize-winning author Kenzaburō Ōe wrote two novellas, Seventeen and The Death of a Political Youth, that were obviously inspired by Yamaguchi's actions, although he was not mentioned by name.

Yamaguchi's actions and the massive publicity they received inspired a rash of copycat crimes, as a number of political figures became targets of assassination plots and attempts over the next few years.

In this incident, Kazutaka Komori, a 17-year-old member of the Greater Japan Patriotic Party, attempted to assassinate the president of Chūō Kōron magazine for publishing a graphic dream sequence depicting the beheading of the emperor and his family.

As Yamaguchi rushed Asanuma, Nagao instinctively adjusted the focal distance of his lens from 4,5 m (15 ft.) to 3 meters (10 ft.) and captured an extremely clear image of the assassination.

[3] On December 15, 1960, a large number of Japanese far-right groups gathered in the Hibiya Public Hall where the assassination had taken place to hold a "National Memorial Service for Our Martyred Brother Yamaguchi Otoya.

"[3] The Greater Japan Patriotic Party has continued to hold an annual memorial service for Yamaguchi every year on November 2,[4] the anniversary of his suicide.

[3] On 12 October 2018, Gavin McInnes of the Proud Boys, along with members of the group, participated in a reenactment of the 1960 assassination at the Metropolitan Republican Club.