Vagrant transfer student Ryuko Matoi, who wields a scissor-shaped longsword that can cut Goku Uniforms, challenges the council as she searches for her father's killer. Although she is initially easily defeated by Takaharu Fukuroda, she finds a sentient sailor uniform that she names Senketsu, a Kamui (神衣, lit. "Godrobe") which is completely made of Life Fibers and transforms her so that she can face Kiryuin and her trials and obstacles. Ryuko is befriended by her hyperactive classmate Mako Mankanshoku, a no-star student, and moves in with her impoverished family.
When Satsuki reorganizes the allocation of Goku Uniforms through a battle royal and king-of-the-hill event known as Naturals Election, Ryuko faces the members of Satsuki's Elite Four, who wear powerful Three-Star Goku Uniforms, in a series of duels. After defeating three of her opponents, Ryuko's final fight is interrupted by Nui Harime, the wielder of the other Scissor Blade, revealing herself to be the murderer of Ryuko's father. In the ensuing fight, Ryuko becomes enraged at Nui, transforming into an uncontrollable monster in the process. Mako calms Ryuko down, while Satsuki prohibits Nui from entering Honnouji Academy. Ryuko becomes reluctant to wear Senketsu after the fight, until a disguised Nui convinces her to put Senketsu on once more. Nui promptly defeats Ryuko, shredding Senketsu in the process, but is confronted by Satsuki before she can kill Ryuko, and flees.