Even though she's right next to me, my liberal arts sister seduces her big breasts by holding her in close contact with her whispers dirty talk slut

As a university student, I was invited to my girlfriend's house for the first time and introduced to her younger sister Hina. Hina-chan looks plain and serious, and seems shy and speaks less. That night, she was united with her, but Hina, who had passed me in the hallway, suddenly approached me and whispered in my ear, "I'm more sexy than my sister..." and slipped her hand into my crotch. He then smiled as if toying with me, and repeatedly uttered obscene words that he couldn't imagine from his appearance, and began to show his lewd nature...