After coming back from Moscow, Ishii started his political activity at the Socialist Democratic Federation (Japan) (SDF).
He utilized the investigative function of the diet and headed an anticorruption task force known as the "G-Men Squad" within the DPJ.
[2] In 2000 Ishii opposed the screening of Battle Royale, which portrays students that kill each other until only one is left,[3] and asked Tadamori Oshima, the Minister of Education at that time for the government opinion towards the film in the 150th Diet.
Masajuro Shiokawa, the Finance Minister at that time, refused to comment, claiming that Ishii was merely expressing an opinion.
Spurned by the legislative process, Ishii wrote a book about his discoveries, Japan's Secret Checkbook: The Truth about the Financial Interests That Will Destroy the Nation (2002).
Ito escaped down the road covered in blood in broad daylight and fled to the mountains without being noticed, but surrendered himself the next day.
[6] After Ishii's death, a by-election was held in Tokyo 6th District on 27 April 2003, and Yoko Komiyama of DPJ was elected to the House of Representatives.
[4] In 2008, Ito renounced his sworn testimony that there were "personal" motives for the assassination, and then claimed that he had been hired to kill Ishii.
In October 2010, Asahi TV aired a primetime special on the murder, and an expert claimed that forensic evidence showed Ito was attempting to seize Ishii's briefcase.
Hosaka has noted that one disturbing detail is that reporters had called him asking about Ito immediately after the murder, a day before any suspects had been announced.