The Karen Bee arc serves as a sequel to the Nadeko Snake segment from Bakemonogatari . While Karen is a self-proclaimed "hero of justice," the arc explores the difference between "real" and "fake" justice. Kaiki represents the "fake" supernatural, yet his impact on Karen is dangerously real, forcing Koyomi to intervene to save his sister.
Watch the episode to see Koyomi's race against time to save Karen from her supernatural fever: Nisemonogatari Karen Bee, Part 4 - Watch on Crunchyroll Crunchyroll• Jan 28, 2012 Nisemonogatari Episode 04: Karen Bee, Part 4 4 : Karen Bee, Part 4
The episode picks up after Karen has been afflicted by a supernatural "Wreathe-Fire Bee" oddity. The Karen Bee arc serves as a sequel