Kōsei and Nagi perform a set piece written for piano four hands. During the performance, Kōsei competes with Nagi to see if she can keep up with him. As Nagi believes that she understands Kōsei on a deeper level, this pushes her to perform with all her heart. After they end their set piece, the audience is blown away with their performance. While backstage, Kōsei is confronted by Takeshi, who is jealous that Kōsei teamed up with Nagi, otherwise known as his little sister. Takeshi demands Kōsei the chance to beat him in an upcoming piano competition. Kōsei visits Kaori on the roof of the hospital to find her passion for music awakened, since she listened to Kōsei and Nagi's performance from her phone. Kōsei challenges Kaori to perform one more duet with him.