Piano ~Kouroukan no Reijou-tachi~

Takajou Takumi lost his parents in an accident. The only relative he has in his life is his precious sister, Miu. He and she were placed into a mansion run by their Chinese uncle. There, they meet various girls in refuge, to what they thought they call a "garden."

His uncle designates Takumi to become the successor of the mansion. He has been trying to make him the successor against his own wishes only because his father was a slave trainer. His father has trained many women into becoming successful sex slaves during his days. That bloodline is now passed to Takumi and he is expected to follow in his footsteps or else...

In order to protect his sister, Takumi has no choice but to become the slave trainer of the house...

In this strange relationship of a game of roses and thorns, Takumi is placed between the boundary of trust and morality as he and the girls gradually develop beyond master-and-slave relationship and into tenderness. But when subordination turns into affection, love becomes desire and tragedy ensures...

[Roughly translated from Getchu]

The game is about a group of girls who are sold to a mansion and trained as sex slaves, complete with bondage, incest and rape.

[from http://www.riuva.com/?p=369]