19-year-old female college student Ai undergoes an interview to become an AV actress, but shocks everyone with a surprising confession. She reveals that since childhood, she has enjoyed masturbation by inserting her fist into her pussy. Using this experience, she trains under a beautiful expert in fisting, gradually expanding her vagina. She practices with thick objects like bats and radishes, then engages in consecutive pussy-stretching sex over three days with a man possessing an extremely thick cock. The result? Ai's vagina becomes so stretched that a fist completely disappears inside—an astonishing climax to her transformation.