A man who enjoys his days by living a two-way life without telling his girlfriend. One day, when I went to her house, I found out that the two were sisters. Normally, I would get a cold sweat and have no choice but to avoid it, but I came up with the idea of enjoying the two of them at the same time. A dream-like time is achieved through a speed-shift threesome, with sex with my sister in one room and sex with my sister in the next room.