To view this scene you will have to enter the villa between 10:00am to 12:00pm when Lumina is playing the piano, inside you will find Rock, Sebastian and Romana listening to her play. When she is finished, Romana complements her and suggests she can become a little more creative. After she leaves, Lumina confides to you that she hasn't enjoyed playing the piano lately and that she does not understand what Romana meant to "play freely."
You will then be given two choices: "Just work harder" or "Just have more fun." Depending on your response to her dilemma, Rock will either scold you for being inconsiderate and give her some of his own thoughts on the matter or leave the mansion thwarted. For best results, pick the latter. She will then tell you about her background and then thanks you for making her feel better.