I was supposed to be watching over the yuri couple, but before I knew it, I was caught between them.

Shiina Mio, my childhood friend. Shiraishi Shiho, whom I met in high school. The two of them seemed just like lovers. I thought it was enough to just watch over them quietly. To cheer them on, to encourage them, and someday be able to celebrate for them—that's what I believed. But one day, I saw the two of them kissing in the music room. The next moment, somehow I ended up between the two of them...!? This is a story of how I, who was pure and innocent, was gently enveloped and melted by the two of them, a slightly mysterious love story.