Reimu is defined as unusually easygoing, lacking any sense of danger, and being carefree. She is described as simpleminded, always showing her true feelings and acting on whatever ideas she thinks, She can also be emotional and noisy, and her presence is well known wherever she is, but she can also merge into her surroundings quite easily when necessary. She is portrayed as someone simple who passes her days sweeping the shrine grounds, drinking green tea and lazing about Marisa is an outgoing and informal person. Hieda no Akyuu states that her personality is condescending, but she has a sophisticated side to her that tends to be interesting. She socializes with many inhabitants of Gensokyo and is friendly to both human and non-humans individuals. She's quick to act if she hears or sees anything interesting, sometimes doing dangerous things to satiate her interest at the time like when she follows an eagle on a whim in the middle of a blizzard. She speaks in an informal manner and typically uses the sentence ending particle da-ze~ (ぜ). REMILIA While she tries to cultivate the image of a mysterious and frightening vampire aristocrat, she is surprisingly polite. Her long lifetime has only served to make her prone to boredom and as a result she prizes anything she finds novel, frequently indulging her own childish whims in order to create entertainment for herself. In Silent Sinner in Blue she allows herself to be manipulated by Yukari Yakumo, simply because the alternative would have been boring. The other residents of the Scarlet Devil Mansion spend much of their time catering to Remilia's odd whims (including numerous parties), though she does make an effort to appreciate and respect their patience. Remilia is respected by most youkai of Gensokyo and so she's said to have a charismatic personality. However, in reality this is only because of the fear they have for her kind. While she can act in an overblown and grandiose fashion, she usually only does it during incidents or for important matters. Otherwise, she tends to exhibit childish behavior. She enjoys novel things and isn't above playing along in silly games FLANDRE In Embodiment of Scarlet Devil, she is described as being quite strange and eccentric, which makes it difficult for others to understand her. She's also described as being "normally docile" and generally pleasant to be around, but somewhat of a loose cannon if left unwatched. In Bohemian Archive in Japanese Red, it's suggested that she isn't very good at talking to other people, though she can get rather sassy and uppity when talking with her sister. Her friendship toward humans is very low. In Foul Detective Satori, her attitude was particularly impolite and informal, speaking in a very casual tone and generally doing as she wished without consideration of consequences, although she stopped short of seriously injuring anyone. In Sunken Fossil World, she appeared to only care about "destroying the indestructible" when facing off against Yuuma Toutetsu, although she did display a willingness to work with Okina Matara, insofar as it let her have some fun. Until the time when she met either Marisa Kirisame or Reimu Hakurei in Embodiment of Scarlet Devil, she claimed to not have seen any humans other than when they were prepared for a meal, although it's left vague as to whether that was her idea of a dark joke. During the events of Sunken Fossil World, however, she left the grounds of the Mansion for an extended period of time of her own accord to fight Yuuma Toutetsu, marking her first major departure from the grounds of the Mansion since her introduction. Abilities As a vampire, Flandre possesses superhuman capabilities just like Remilia Scarlet, such as enhanced physical strength, with the destructive power of oni and the nimbleness of tengu, as well as a vampire's bodily and regenerative ability. She can swing an oversized sword, though not as quickly as she would like to.

In Gensokyo, the sky becomes covered in red mist, blocking the sun in the middle of summertime, which becomes known as the Scarlet Mist Incident (紅霧異変). Reimu becomes determined to find the cause of the red mist, as if left alone, the mist would spread across Gensokyo's border to the human world. Marisa hopes that the individual responsible for the mist would have valuable items to collect. Reimu that the mist is coming from the direction of the Misty Lake (霧の湖). Travelling in that direction, she encounters the yōkai Rumia, and later the ice fairy Cirno, determining neither are related to the mist – instead, the Scarlet Devil Mansion (紅魔館), which seemingly appears from nowhere, is discovered to be the cause. The mansion's guard, Hong Meiling; resident anemic witch, Patchouli Knowledge; and time-stopping maid, Sakuya Izayoi, all attempt and stop the intruder from reaching the mistress of the mansion, Remilia Scarlet