A little vampire is trapped in the basement of a mansion for four hundred years, or more. Her sister is thought to be the reason she is suffering, but maybe there is a bigger picture than that. Like an incident...

Flandre Scarlet has always wanted to experience the outside world for herself. Locked away for most of her life because of her unpredictable nature, Flandre grows bored of the same thing until one night, she slips away from the mansion. Along the way she meets the various inhabitants of Gensokyo while both causing and getting caught up in troublesome situations.