Rio comes from Hokkaido. She was Shiina's friend and classmate when they were in elementary school. She is currently hosting cosplay events in Akiba like Nobunaga does.

Since Rio has moved to Tokyo, Shiina have not heard from her, but they reunite by chance when both of them are asked by Yuuto to participate in a cosplay event that Nobunaga organized.

Roughly translated from url=ja.wikipedia.org↗(opens in a new window)