My childhood friend girlfriend keeps count of how many times we've had sex. According to my memory it's been 20 times, but she's saying things like "Today makes 21 times..." Could it be that she's including the times she's been with my twin brother who looks just like me?

My childhood friend girlfriend who keeps count of how many times we've had sex. According to my memory it's 20 times, but she's saying things like "today makes 21..." Could it be that she's also counting sex with my twin brother who looks just like me? My name is Nishino Yuma. I'm a third-year high school student. I have a twin brother named Yuya. We twins look incredibly alike. Honestly, nobody can tell us apart. Even our mother sometimes says things like, "Are you Yuma or Yuya?" From my perspective, my older brother has sharper, more piercing eyes, while I have slightly droopier eyes. But according to everyone else, that difference is negligible. True enough, if my brother's face is slightly puffy from sleep deprivation, we really do look identical even from my own perspective. One day. With Yuya absent, in my room— well, it's one room for both of us twins, on the lower bunk of the bunk bed, I was about to start fooling around with my childhood friend girlfriend Airi when she told me something typical. "Hey, Yuma. Today makes 21 times." "Huh? 21 times...?" "Yeah. 21 times..." "Wait, hold on. From what I remember, if we do it today, I thought it would be the 20th time..." "That's not it. I'm counting properly..." "But I mean, I always count before we do it too, and I remember it properly..." At that moment, a terrible feeling ran through me. "Did you sleep with my brother!?"