Yuriko Sagara begins assisting Koyama, a middle-aged male colleague who asked for her help with his sales duties. Gentle and kind, Koyama gradually captures Yuriko's heart. One night, while working late together, a sudden thunderclap startles her, causing her to instinctively cling to him. Her innocent reaction stirs growing excitement within Koyama. With the office plunged into darkness by a power outage, he reaches for her in the shadows. Though she resists at first, his advances overwhelm her sincerity, and she surrenders her body, succumbing to waves of pleasure.