Frau Kojiro is a key character in Robotics;Notes, known as the genius programmer behind the popular fighting game Kill-Ballad. Her real name is Kona Furugōri, which she keeps hidden.

The character’s background is deeply tied to the mysterious past of the anime series Gunvarrel. Frau is the daughter of the director of Gunvarrel, which is later revealed to have been a covert propaganda tool used for mass brainwashing by the Committee of 300. When the show's staff discovered this truth, they were eliminated. Frau only knows that her mother disappeared and was last seen on Tanegashima, which becomes her primary motivation for becoming involved in the story.

In the narrative, Frau is recruited by Akiho Senomiya to join the robotics club at Tanegashima Technical High School. Her exceptional programming skills make her an invaluable asset when the club decides to build a giant replica robot based on Gunvarrel, named the Gunbuild-1. Her role in the club goes beyond simple membership, as her creation, the Kill-Ballad game, is also a key interest of the protagonist, Kaito Yashio. Throughout the plot, Frau aids the club in their engineering challenges while also searching for clues about her mother’s fate.