It all started when her older sister sent us a photo of herself masturbating.
Spurred on by the dirty messages, we ended up losing our virginity to each other on the school rooftop.
When we confronted her, asking why she’d do something like that, she flipped the script and suggested we film ourselves having sex and exchange the videos.
That was the beginning of our “Voyeur Alliance.”
With every voyeuristic message we received, the things my girlfriend and I did—and the things her sister did—escalated. The thrill of filming our own acts and the sweet anticipation of receiving a reply became an irresistible trap. Our desires spiraled deeper and deeper.
Our secret game of Play by Mail—watching each other, craving more.
Even now, my phone buzzes with images of those lewd women.
So… what should we do for fun today…?

[Translated from bangumi]