Someone is trying to kill Maejima, the unassuming Archery club adviser and Math teacher at Seika Women's High School. What appears to be pure, dumb luck has gotten him through several attempts unscathed, but he has no clue as to the perpetrator and the Principal would rather not involve the police in what's "surely just a student acting out". With the entire faculty and student body as his suspects, Maejima struggles to discover the culprit before his luck runs out.