Sister Magic!

The main character lives with his three younger sisters, Haruna, Nano and Nonomi. They don't care about him, so they often walk around the house without clothes or come into bathroom while he is bathing. He is confused by their demeanors and suddenly starts having a dream of a girl who taunts him without notice.

One day, the girl in his dream - whose name is Nerisu - suddenly appears. According to her, she is a princess of the devil world and he is a prince. This means he is the one who will take over the throne. He soon finds out that his three sisters are aware that they are actually descendants of a magician.

There is only one way to stop him taking over the throne: If one of three sisters gets pregnant with his baby, he won't have the need to do so. The sisters soon curse him to not to be able to ejaculate without them. A fierce battle for him and his babies now breaks out...

[From ErogeShop]