A lewd and innocent love story about a guy who had sex with his girlfriend's idol sister while she was away on a four-day trip. (MIDE-670 by Takahashi Seiko)

My live-in girlfriend's older sister is the entertainer, Seiko Takahashi. One day, the three of us were drinking together. That night, my girlfriend got drunk and lay down to sleep, leaving only Seiko and me. In the middle of a quiet moment, Seiko suddenly kissed me deeply. After that, although we didn't see each other, Seiko would call me whenever my girlfriend went on a trip…