In a world called Septpia, Yoshichika Tsurugi is a teenage boy who lives in a cottage in the city of Naien with his younger sister Shiori Tsurugi and father Rentaro Tsurugi. As a paradox zone appears in the city, logicalists Tamaki Yurine, Chloe Maxwell and Mana Asuha manage to defeat a dog-like demon god named Cerberus, turning it back to a human and dog...