PARK CITY976 Archives Utah -- There's a scene in Tokyo Idolswhere Rio Hiiragi, a pop star trying to make it big, bikes to small provinces as a publicity stunt to meet her fans. She's wearing a cute yellow helmet and live streaming her trek. Trailing behind her are a handful of older men. They are her biggest fans. 

The documentary premiering at the Sundance Film Festival spotlights the world of young female performers -- "idols" -- who dress like anime characters and sing and dance for adoring crowds, even though many aren't very good at singing or dancing.

It's more important for idols to be cute and tender to fans than sing well. 

The idols are beloved for their innocence by middle-aged men who call themselves their "brothers." They make glittery t-shirts, spend $2,000 a month on idol-related merchandise and events, attend near daily performances, and long for the opportunity to hold their favorite girl's hand during timed meet and greets -- even though they won't talk to women during their daily lives.

"It's really about that ephemeral quality of girlhood," filmmaker Kyoko Mitake said during a Sundance Q&A, going on to add later that "the fans have this almost, the illusion, [as if] these girls are their girlfriends." The girls' lyrics can even center around empowering the socially awkward.

In Japan there are 10,000 idols making up a billion-dollar industry, which is distinct from the general music scene. There are mainstream idols and underground idols and some, like Rio, dream of shedding their idol personas to become legit music artists. The idols livestream twice a day, tweet incessantly and perform daily, often not making enough to get by as managers and venues profit.

Last 1 about Tokyo Idols, from Miyake on growing up in Japan: "Not being or acting cute was taken as an act of defiance" #Sundance

— Brittany Levine (@brittanylevine) January 21, 2017

The brothers, also known as "otaku," speak of failing to achieve their own dreams so they strive to help realize those of their idols, who are as young as 10. Twenty-one is considered the end of the road. 

While the film aims to focus a critical eye on the idol industry and its impact on the girls, the best scenes spotlight the otaku -- a catchall term for pop culture super fan. It's also used to describe idol devotees. Once a diss, otaku has risen to be a badge of honor (although they still have their critics and admit to being socially challenged outside of the super fan community).

As otaku culture seeps into the mainstream, more men are letting loose at idol concerts, shaking glow sticks and dancing until they sweat profusely. Adult men aren't the idols' only fans -- they are also beloved by women and girls, too, but their presence is limited in the film.

For the most-devoted otaku, their idol is their life. During Rio's 21st birthday concert, her fan club collected donations for presents and gave her a cake. She blew out the candles on stage as the crowd sang "Happy Birthday." Their de facto leader even gave a raspy speech before leading a fervent chant of "Encore!"

"This isn't a fad, it's a religion," a commentator in the film aptly remarked.