The Mukai siblings lost their parents at a young age. Ai, the older sister, continued to work hard, graduating from junior college and becoming an office lady. On the other hand, Taichi, the younger brother, liked to play around and didn't study much, but Ai Ke'ai Taichi, her only family member. One day, Ai gets a call on her cell phone from a man named Nakata. He says, "Your younger brother has ruined the boss of our gang." Ai is called in to settle the score, where Nakata and his men violate her in front of her younger brother, and even forces her to have sex with him...