"I'll change you." When Yumiko, age 23, hears her crush (who has no idea how she feels) is engaged, she throws caution to the wind and decides to have a crazy night on the town! There, she gets picked up by a guy called Kikuo, who takes her to... a swingers' bar!? She escapes, but who should join her company the next day but Kikuo himself...! As Kikuo prods her to break her crush's engagement, Yumiko gives in and lets Kikuo school her in the ways of pleasure... Playing with Kikuo, and engaging in some mutual rebound sex with her manager Toshi... What's going to become of her office life now!? And what'll happen with her crush...!? This is a love story revolving around Yumiko, a straight-laced office worker gone astray.