I'm curious how this girl became the runaway most popular character of the new Idolmaster set.
A mixture of factors, she has big underdog appeal since at the beginning of the story she was literally bottom of the class along with China and Ume so it made people want to root for her. She's a pretty amusing character thanks to her eccentric personality and soft and sometimes deadpan voice, giving her an innate multiplier on any jokes she delivers. The story made many jokes at her expense at first since her total lack of physical stamina, singing ability and coordination meant she could barely perform or even train without keeling over exhausted, which makes it all the more satisfying to see her improve, take the stage for the first time and even go further beyond what anyone ever thought she was capable of.
Her card decks are also typically quite difficult to play compared to other idols; her base HP is among the lowest in the game and her decks usually have stricter activation conditions on their special abilities, so actually playing Hiro is inherently more challenging - tying perfectly into her story depiction. Hiro's producer puts his career on the line gambling on the success of a literal bottom-tier idol despite everyone telling him not to (including Hiro herself).
In the story her in-world fans are even described as "weirdos" lol.
