I'm dating a girl who isn't pretty but has a nice personality, and I've started thinking about getting married... One day, I go on a trip to a hot spring with her best friend and her couple, and when I meet her for the first time, I fall in love with her at first sight because she's my ideal type. However, when I find out that she's engaged to her boyfriend, I'm heartbroken. That night, I see Yuna's beautiful body in a mixed-gender hot spring, and even though I know it's wrong, I force myself to have a relationship with her...