Tesura Nishina does not reason

The story begins with an image of a girl standing atop a bridge guardrail, but flashes back a few days before that, when a girl on a train accuses a salaryman named Shunta Momochi of molesting her. Another girl named Tesura Nishina raises her hand and comes to his defense, solving the incident before the girl and Shunta get off the train. Together, the "unreasoning" Tesura Nishina and Shunta Momoichi, who just wants to be friends with a high school girl, will explore what Tesura calls "meaningless theories," her term for the mysteries of everyday life.