Days with My Stepsister, Vol. 3 (manga)

I can t fall in love with her. After all, the two of us are siblings. It s Yuuta and Saki s first summer break as stepsiblings. Now that Saki has started part-timing at the bookstore where Yuuta works, they inevitably end up spending more time with each other. After being around his little sister a lot more than usual, a forbidden emotion starts to well up inside Yuuta s heart...