[1] Kuroki, a reporter for the trade paper Tekko Shinpo, is investigating the arms manufacturer Mihara Industries on suspicion of the illegal trafficking of weapons from Japan to countries in Southeast Asia.

He notices some foreign visitors leaving the company and discovers that they are purportedly visiting in order to attend an exhibit sponsored by Toyo Arts Society, which is led by Takayama Hiroshi.

Takayama admits that Natsuko worked for the Japanese-Russian League and was killed and made out to be a prostitute for refusing to gather information for the allies but continues to warn Kuroki to drop the story.

In an interview with Chris Desjardins in the book Outlaw Masters of Japanese Film, Fukasaku explained that The Proud Challenge "was meant as an exposé of the CIA's plot to crush the Communist and socialist left in Japan.

"[3] Reviewer Patrick McCoy of the website Lost In Translation wrote that The Proud Challenge "grabs the viewer's attention immediately" and concluded that "the film is a suspenseful thriller that offers a critique of political corruption, hypocrisy, and journalistic cowardice in postwar Japan.

The final scene suggests that the entire fabric of Japanese democracy is controlled by American interests aimed at crushing the socialist left (Toei's conservative managers seriously objected to the wider implication of the movie and put Fukasaku on probation for six months).