Ep. 3: Jin and Nagi investigate a mysterious impurity in the art club storehouse

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Jin, Daitetsu Hibiki, and Meguru Akiba are assigned to clean an old storehouse by their art club seniors. Jin discovers a spider-like impurity but conceals this from Nagi. Suspecting his behavior, Nagi borrows Tsugumi's spare uniform to infiltrate the school. She accompanies Jin and his classmates to investigate a mysterious knocking sound from the cellar, only to discover it is a teacher whose studio is located beneath the floor. Nagi persists in her search for the spider-like impurity and instead encounters a mysterious girl who calls Nagi her older sister. This girl effortlessly destroys the impurity, leaving Nagi with more questions about the strange occurrences at the school.