Onee-chan To Shota-kun To. ~naka O Yoku Suru H No Kankei~

Our young male protagonist Shouta is really warmed up for his step-sister Azusa and wants to woo her into a fuck session, but she behaves pretty cold towards him and avoids his attempts. She calls her girlfriends for a sleepover while their father is on a business trip and one thing leads to another.