TV-Series
Description
Yū Abiko, known as Biko, is a magic tool artificer. She attended Magic Law School with Toru Muhyo, Yoichi Himukai, and Soratsugu Madoka (Enchu). Academic records show she failed English and Japanese but excelled in science. Initially disliking her strict teacher, Rio Kurotori, Biko's feelings transformed when Rio shielded her from a chemical explosion Biko caused, sustaining severe back injuries. This fostered deep admiration and loyalty, leading Biko to become Rio's apprentice in magic tool craftsmanship.

Biko is short with medium-length blond hair and red eyes. Her typical outfit includes an orange hat, green scarf, and long striped dress; the hat often leads to her being mistaken for a boy, as happened when she met Jiro Kusano. Personality-wise, Biko is deeply devoted to Rio, calling her "Teach." She is generally quiet but fiercely protective if Rio is criticized. She likes cheese gratin (especially Rio's), raisin bread, and fruits like strawberries, while disliking running, carbonated drinks, and long talks. Her talents include cleaning, disassembling/repairing objects, and unintentionally zoning out.

As an artificer, Biko creates magical tools but cannot activate them herself. Her craftsmanship produces legendary artifacts like Temper Root Water, a restorative potion that replenishes life energy but is lethal in excess. Other creations include portable magical law seals, magical traveling seals, smoke bombs, and the Yuurenmin Merry, which accelerates magical energy recovery. Her tools function best when the creator's power level matches the user's. After her apprenticeship, she established her own workshop and trained three apprentices.

Biko's narrative centers on her bond with Rio. When Rio allied with Enchu and betrayed the Magic Law Association, Biko maintained faith in her redemption. During the Arcanum Prison incident, Rio demanded Muhyo's surrender; after Rio was subdued, Enchu and Teeki abducted her. Later, in the Wailing Vale arc, Biko confronted Rio after learning Teeki orchestrated the spirit attack that killed Rio's mother. When Rio expressed suicidal despair over her crimes, Biko slapped her, insisting guilt wasn't enough and advocating for atonement through living. Biko articulated her hope for their future, mentioning baking bread and picking raspberries together. After Rio defected from Enchu and faced trial, receiving indefinite suspension and house arrest, Biko assumed responsibility for her supervision. They cohabited with Judge Reiko Imai, who monitored the arrangement.

An extra comic within the sequel manga implies Biko experiences romantic attraction toward both Rio and Enchu. This adds dimension to her interactions, particularly her unwavering pursuit of Rio's rehabilitation despite Rio's actions as an antagonist. Her development transitions from a student reliant on Rio to an independent artificer mentoring others, while her emotional journey centers on reconciling loyalty with moral conflict.