DEEMO Memorial Keys

Alice, a taciturn and withdrawn girl, attracts everyone's attention with her piano. But something changes in her heart after she meets Sania and Rosalia. At the same time, a little girl falls from a window located high in Deemo's castle. Although she loses her memory, she somehow knows the name Deemo. She also meets Mirai, Nutcracker, and Fragrant Sachet in the castle. To cultivate a sacred tree by the melody of piano so that the girl can leave the castle, they decide to collect sheet music all over the castle. While they are looking for sheet music, the girl meets Masked Lady. What is the relationship between them?