Remilia and Flandre

While she tries to cultivate the image of a mysterious and frightening vampire aristocrat, Remilia is as childish as her appearance suggests. Her long lifetime has only served to make her grow bored more quickly, and she prizes anything she finds novel. In Silent Sinner in Blue she allows herself to be manipulated by Yukari Yakumo, simply because the alternative would be boring. The other residents of the Scarlet Devil Mansion spend much of their time catering to Remilia's odd whims (including numerous parties), but she appreciates their efforts and treats them with respect.

Flandre is rather nice and quiet, but somewhat anti-social. She typically stays inside, thus worsening her social skills, leading to her staying inside more, creating a feedback loop of isolationism. She is said to respect her older sister a lot. Flandre, unlike most vampires, is exceptionally bad at feeding herself. Due to her immense power, when she tries to attack a human, she vaporizes them completely, leaving their blood coating anything nearby and firmly inedible. She depends on the mansion's maids—primarily Sakuya—to feed her.