A secret between me and Kana-chan that I'll take to my grave. My best friend's girlfriend was so cute in her defenseless, makeup-free state that I impulsively slept with her that night

The doorbell rang in my small room, which is already small enough for one person. Who could it be at this hour? When I opened the door, a woman I knew was standing there. Her name was Kana. A friend from our student days, my best friend's girlfriend. …"Let me in." She entered the house rudely, without saying much. It seemed she had left home after a fight with him. She changed into her loungewear, and we had some cheap liquor and instant ramen. "It's like we were students again. Thanks for listening to me." A slightly tipsy Kana leaned against me. Her slender shoulders, her defenseless cleavage, made me intensely aware of her as a woman.