With her mother unable to come, my girlfriend's adult younger sister joins her older sister and me on a hot-spring trip. Whenever she gets me alone, she presses her body against mine, caresses me, and begs for a kiss. As soon as I get hard, she sucks my cock until I am ready to blow, then takes it in position after position and makes me shoot a huge load whenever she wants. I am humiliated by how completely she controls my orgasm.