You're Back, Onee-chan - S1.E1

After school, Akira Sakagami is about to ask his classmate, Nana Shirayuki, out on a date. It was going well until his sister, Rio, appeared on the scene and put a damper on his plans. For Akira, Rio is not only his sister but also his first love. Rio used to live alone, but due to her housing situation, she has moved back home with Akira. When Rio tells Akira that Shirayuki looks like him, Akira sees Shirayuki as Rio.

Later that night, Akira is caught masturbating by Rio. Akira froze, but Rio was unfazed and made fun of the actress he was using as a joke, saying she looked like her. Not stopping there, she grabs Akira's penis.