An investigation by BBC Eye exposes the men profiting from an ugly business of sexual assault for sale.

We find websites selling thousands of videos of men sexually abusing women on trains, buses, and other crowded public places across East Asia. You can even order your own tailor-made assault on these sites.

They’re run by a shadowy figure known as “Uncle Qi”. He’s hailed as a guru by an online community of perverts. But who is he?

The hunt takes Assignment to Japan, where sexual assault in public is known as "Chikan". We take you inside this dark and twisted world to hear from the perpetrators of these horrific crimes, and meet the women who are fighting back.

The investigation goes undercover to expose the identity of the men running these websites who are cashing in on sexual violence.

Presenter: Zhaoyin Feng

This programme deals with matters of a sexual nature which some listeners may find disturbing.