My step-sister [Mitsuki], the daughter my parents brought from their remarriage, is a diligent and cute girl who's popular with everyone. I was living happily with such a sister. One day, both of my parents left for a day trip starting in the morning. As a result, Mitsuki and I were alone together for the whole day. Although we were living as usual, when it was just the two of us in the living room, Mitsuki, who was always cute, started acting strange. She would kiss me with saliva dripping, show off her masturbating, even come to wash my body in the bath, and aggressively try to take my body... What should I do!
