Mitsuki is a patient at the local hospital that suffers from amnesia. This was triggered by a certain circumstances in her past. She previously had with her younger sister, Shiho, a flower shop as a gift until they've shut down due to Mitsuki's severe allergic reaction called Anaphylaxis. The fact that she has allergic reaction, she still adores flowers so much she eventually began to suffer severe depression which had caused losing her memory, not able to recognize her younger sister.