The Japanese 'idol' and the superfan who's twice her age

There are about 10,000 young women and teenage girls in Japan who have a huge following and are known as 'idols'.

Rio is one of them, and superfan Koji goes to great lengths to support her. They explain why they need each other.

Rio and Koji's story is featured in Storyville: Tokyo Girls which was first shown on BBC Four. Viewers in the UK can watch the full film here.