Yu Abiko (我孫子 優, Abiko Yū), commonly known as Biko (ビコ, Biko) is an Artificier. She is very skilled at making Artifacts, and was even able to make the legendary Temper Root Water.
Biko has a great admiration for her teacher, Rio. She affectionately refers to Rio as "Teach". While wearing her hat, Biko looks like a boy, so many people mistake her as one. Roji, for instance, instantly thought Biko was a boy, until Rio removes Biko's hat.
Biko was originally a student at Magic Law School with Muhyo, Yoichi, and Enchu. According to the Author's Q&A, Biko failed English and Japanese, but excelled in Science class. Her teacher was Rio, but Biko didn't like her at the time. One day, Biko was called up in front of the class to demonstrate an experiment. Rio noticed that Biko was pouring the chemicals incorrectly, and pushed Biko out of the way, hurting herself in an explosion. Biko then developed a love for Rio, wanting to be taught by her. Eventually, Rio trained her to be an Artificier.