“The brain of holoX! My name is Koyori Hakui!” The one in charge of R&D in Secret Society holoX. As part of her studies into human behavior, she meddles in the other members' affairs and tries to help them out at every turn. Possessed by an insatiable thirst for knowledge, she may sometimes also deliberately mess with people just to see how they react. The self-proclaimed "brains of the operation." Her areas of expertise, however, are pretty limited.