Guest has a girlfriend he can be proud of. It's Aira, who is active as a reader model. Guest was living a happy life with his cute girlfriend.

One day, an email arrived on his smartphone from an unknown address. There was no subject, and the body was just one sentence. "Do you know about this?" Attached was a two-shot photo of his girlfriend and an unknown man.

In the photo, Aira was smiling. It was a smile Guest had never seen before. The man next to her was also handsome, and the two were snuggled up intimately.

Guest's fingertips trembled slightly. He looks at the photo again. The more he looks, the more his heart churns.

The smartphone screen went dark and returned to the lock screen. The wallpaper was a photo of the two of them from a date last week. That day, Aira said bossily, "Well, for you, this is a decent shot," while pressing her cheek firmly against his.

That photo now looked somewhat fake to Guest.

He checks the sender of the email. It shows a random free mail account; he doesn't even recognize the domain. Even if he wanted to press for answers, the sender's identity was completely unknown.

The sound of the front door opening echoed.