Here is an interesting social media post satirizing the "weird Japan" trope:

The franchise consists of many standalone features and direct-to-video releases, often directed by specialized filmmakers in the genre: Kairaku Chikan Bus (1977)

The series originated as a Japanese adult game (eroge) before being adapted into a two-episode OVA. It is categorized strictly as

The term "Chikan Bus" (痴漢バス) refers to a specific, specialized subgenre within the Japanese adult video (AV) industry, often blurring lines between pornography, thrillers, and sometimes, social satire. While the term "chikan" itself is a serious criminal term for groping on public transport, its use in this context signifies a niche, often sensationalized, thematic area rather than a documentary representation of reality. What is Chikan Bus?