To some up Kiss x Sis, it would be safe to say that it is an incestuous, harem manga that makes you feel dirty, like really dirty. It has forbidden romances, pee scenes, along with raunchy saliver play. If you are a little kinky, I would recommend this.
The story is about Keita, and his two step sisters Riko and Ako. He works hard to get into the same high school as him, whilst they do everything in their power to win the battle for his love. They jump on him and kiss him with every turn, trying to get his attention. At school it only gets worse. he has a teacher and two students after him, along with Riko and Ako visiting him. Overall, it is chapter after chapter of sexual tension.