Impure Relationship - Fujun na Kankei

One day Shiori entered her brother Hayato's room and found him look at a dirty magazine with his friends. She took the magazine away from the boys, scolding him. Shiori becomes curious about the ero magazine her brother had been looking at then began to masturbate to the magazine, eventually passing out from or orgasm. Hayato comes in and sees what happens, and helps himself to his sleeping sister.

A switch is turned on inside both Hayato and Shiori, and they become lovers, stealing secret sex or fellatio or petting whenever they can.

There are 9 chapters in this long and awesome story, with the entire story being told in this one volume. The story is part of the awesome Onee x Shota or Straight Shota genre.