A mass stabbing incident occurred 6 August 2021, on a commuter train in the Odakyu Electric Railway in Tokyo, Japan.

In 2016, 26-year-old Satoshi Uematsu committed one of the most serious incidents of mass murder in Japan since World War II, when he stabbed 19 severely disabled people to death at a care center.

Two months after the attack, 24-year-old Kyota Hattori, who dressed as Joker, committed attempted murder and arson in a Keiō Line train at Chōfu in October, resulting in 17 passengers being injured.

At around 8:30 pm (JST: UTC+9) on 6 August 2021,[2] Yusuke Tsushima, aged 36,[1] began stabbing people indiscriminately on a commuter train in Setagaya Ward.

[17] Although police opened an investigation, Tsushima was quoted as saying that he had been wanting to "kill a happy woman for the past six years"[11] and added that the day of the incident "anyone would have been OK".

[19] On 8 August 2021, Tsushima was sent to the prosecutors, where he said that he was ultimately motivated to commit the crime when he faced online rejection from women and regretted that he had not killed anyone, quoted as saying that the fact that no one had died was "unfortunate" for him.

[20] On 10 August 2021, Tsushima reiterated his intent to target "happy-looking couples" in his attack and told police he considered bombing the famous Shibuya Crossing in Tokyo.