I have been in love with Rio for a while. I love her very much and promised to marry her. But until Rio had to go on a three-day business trip, Miru – Rio's younger sister, accidentally dropped the keys and had to stay at my house temporarily. During that time, I was seduced by Miru. Although I felt extremely guilty towards Rio, Miru's beauty and charm made it hard for me to resist. I quickly became drained by Miru, and I gradually developed feelings for her. I thought these three days would be the hardest of my life, but no, they turned out to be the best three days of my life...