The girlfriend I made for the first time in my life was a college classmate. We haven't had sex yet. Her younger sister, Erika, is taking exams next year, and since I'm good at math, I've become her tutor. I thought, "I get paid, and I get to go to her house, lucky me," with a light-hearted attitude, but Erika, the younger sister, teased me, a virgin, and tempted me by showing off her breasts...
