The protagonist Kaji is in a secret relationship with his kind and popular boss Muramata-san. He becomes jealous after hearing about her ex-boyfriend from colleagues. He confesses his insecurity to her, saying he wants one of her firsts too. Muramata-san, who is deeply in love with him, shyly suggests trying anal sex as her first time in that way. Kaji carefully prepares her, and they engage in passionate anal sex with lots of affection and pleasure