In the school infirmary, Chacha, a notoriously delinquent gyaru student, skips class as usual. That day, the infirmary's supervisor, teacher Yuriko Shirayama, confronts her about her poor grades and behavior, scolding her sternly. But Chacha snaps, suddenly grabbing Yuriko by the throat and choking her into unconsciousness. Yuriko's eyes roll back, her body goes limp. Indifferent, Chacha leaves her behind. Later, Yuriko regains consciousness—only to discover the choking has awakened an unexpected, intense pleasure within her. The next day, she seeks out Chacha again while she's skipping class. Just as Chacha attempts to strangle her once more, Yuriko counters, swiftly gloving her hands and choking Chacha into blackout. Determined to make Chacha experience the same euphoric thrill, Yuriko revives her and begins what feels like a "choking lesson"—a terrifying, intoxicating cycle of suffocation blending dread and ecstasy. Though Chacha resists at first, she cannot withstand Yuriko's relentless technique. Amid pain and pleasure, she gradually transforms into Yuriko's obedient choking slave.