Koyomi Araragi can't stop thinking about Tsubasa Hanekawa, the brilliant-yet-modest class representative who always follows the rules, but what the boy doesn't know is that beneath her facade, Tsubasa harbors an extraordinary amount of pent-up stress. Things change one day for the girl when she encounters a supernatural feline that allows her to break free from her normal self... causing immense chaos in the process! Luckily for Tsubasa, Koyomi will do anything to help a friend and he sets forth on a mission to return her to normal by any means necessary, leading to an unforgettable Golden Week.