Shiori Kamisaki is the younger sister but the stepson of this guy's stepfather. When the two parents got married, suddenly the two cousins lived in the same house and not only that, because the house was wrong, the two brothers had to sleep in the same bed, in the same room. The fire near the straw was also sharp for a long time, the two sisters developed feelings and then they made love like real couples and no longer half-brothers. The two children often secretly have clumsy sex with each other even when their parents are at home, because they find it very harmonious to have a bed that helps both of them to orgasm many times.