Misaka_Yumi is a Japanese cosplayer who has made multiple appearances in both the A Certain Magical Index anime and manga, as well as its spin-off series. Her most prominent appearance was during the Tree Diagram Remnant Arc where she interposed herself alongside Saten Ruiko to ask questions to clones who disproved her answers and then slapped them as soon as they disproved. Misaka_Yumi quickly became fan-favorite due to her charming yet playful personality which inspired many fans to dub her “Biribiri”, after her signature sound that generates electricity when she generates electricity herself.
She also features prominently in the Touma Index arc, aiding Kuroko Tetsuya in breaking through one of Endymion’s explosive bolts by producing electricity herself – giving her an advantage in combat and giving rise to her intense rivalry with Touma, whom she nicknames “Biribiri.”
Though she often finds Touma difficult, she harbors feelings for him and attempts to obtain his contact info in hopes that one day they can be together.
She can use railgun and electric attacks, magnetically attract iron particles into a chain-sword whip and manipulate electrical objects. During her fight against Gunha in Episode Two of Touma Index arc, she demonstrated her abilities by creating an electrical shock with only one slap of her hand; which was enough to incapacitate and shock Gunha instantly.