えっ！？マジで？ヤリチンの先輩のビッチなセフレはボクの姉だった！バイト先の先輩が見せてくれた最近出来たセフレの写メに写っていたのはボクの姉！？小中高と校則の厳しい学校育ちの姉は超堅物でクソ真面目。だらしないボクにいつも口うるさく説教してくる正直ウザイ…

My Big Sister Went To A Very Strict School From Grade School To High School, And So I Thought That She Was An Ultra Prim And Proper Lady. And She Was Always Scolding Me For Being So Sloppy, And To Tell You The Truth, She Was Getting On My Nerves...

My Older Sister Was In The Picture Of A Saffle That My Senior At Work Showed Me! My Older Sister, An Ultra-straight-minded Fucking Serious Who Is Always Talking To Me, Was Glad To Be Cheated By The Opposite Sex For The First Time In College, And She Became A Yariman Immediately! A Senior Invited Me To 3P Next Time When I Was Shocked! I decided to participate because I wanted to mess with her older sister. On that day, her older sister was surprised and tried to run away, but she caught her and had a threesome with her senior.