Flandre Scarlet is a vampire who stays cooped up in her room deep down in the Scarlet Devil Mansion. On the floor sits a forgotten toy piano.

The piano is a keyboard instrument whose hammers strike strings to create sound. The idea for such an instrument reached the ears of an organ craftsman, who went on to make one. Pianos have taken many shapes over the years, before becoming the instrument we know today. The piano's versatility has led to it being used in education and a variety of other ways. It also inspired the creation of countless new instruments, including those that create sound using air or electrical signals.

Happy Prism Parade! "I can't get their music out of my head," said Flandre to Sakuya as she clutched her knees to her chest, hidden away in her room. It was at that moment, her eyes fell upon the toy piano sitting on her floor. She tapped the keys lightly, and her eyes began to light up.

Having improved her piano playing little by little, Flandre emerged from her room in search of a harmony battle opponent. First, she challenged Sakuya. She won, but couldn't help but feel Sakuya had taken it easy on her. Next up was Patchouli, which ended much the same, but when Patchouli saw doubt in Flandre's eyes, she, too, felt rather upset. Flandre then went to challenge Meiling, but when she found her sleeping by the front gate, she decided to leave her be.

Even alone, Flandre didn't give up and continued to practice enthusiastically. Until one day, she stood up with a determined look in her eye and began preparing to go out. Where she was headed was unclear, but why she was going was obvious. If there was no one to battle in the mansion, she'd have to go out and find someone. But as she gathered her things, she felt as if someone was watching her through the crack in the door.