In preparation for the filming, Hirose and Yamazaki had to learn how to play musical instruments for six months. Hirose plays the role of a carefree violinist Miyazono Kaori who hides a secret related to her past while Yamazaki plays a former talented pianist Arima Kosei who became unable to play the piano after his mother passed away. Hirose revealed that as she started from scratch, it was very difficult for her to learn how to play the violin and she spent an average of two hours per day to practice. As such, she was very excited to be able to share the results of her hard work through this movie. Yamazaki who was also a beginner when he learnt how to play the piano, commented that he had to start from the basics and practised a lot to show the emotions of his character through the piano.