Since her family was out, I went to stay at her place full of confidence. Of course, we were all over each other, and at night, wanting to have sex with her, I gave her a deep kiss. But she resisted, so I looked closely and realized the person I was kissing was her younger sister, Sana-chan. If I apologize right away, that was apparently Sana's first kiss and it's a huge crisis. But Sana had a face that was red and I couldn't tell if she was angry or sad. The next day, when I woke up, Sana came over and said 'I want you to kiss me' with her cute lips.
