"When our story begins, we learn that Seiji was a professional pianist, until three years ago, when he suffered an accident. Since then, he hasn't been able to play the piano professionally. He lives with Yuna, an android, whose the same model as the nurse who took care of him in the hospital.

"Seiji treats Yuna like a human being -- rather than a robot. He has sex with her, he thanks her for her work, and he gives her complements -- as if she were his girlfriend. One day, he decides to teach Yuna how to play the piano. Being a robot, Yuna is able to follow the score without making any mistakes. Excited, Seiji decides to teach her to play like a real, professional pianist -- that means, Yuna must learn how to play the score with subtle nuances and emotion. His effort works, and Yuna learns to perform at a higher level, especially after Seiji takes her to a live concert.