Sasahata North High School is a secondary education facility located somewhere in Tokyo. Chiho Sasaki attends classes here as a second-year student.
Sasahata North is a large high school, the campus consisting of a large stretch of land, and two school buildings joined by a connecting hall. While Chiho's classroom is located in the heart of the new building, classes are still conducted in the old school house across the square, and students are free to move between both. The educational facilities are relatively normal by Japanese standards, consisting of several standard classrooms, an art gallery, and science laboratories housing the usual experimental tools and anatomical models. Like most schools, Sasahata North High School offers extracurricular activities. Chiho Sasaki is a member of the Archery Club, which has a target range somewhere on campus. The institution itself is fenced off by a brick wall and iron gates.
In the anime series, it is mentioned that the school is home to a group of myths known as the "Seven Wonders", a series of local tales told by the students concerning the school's oddities. According the Chiho Sasaki, these stories include a piano in the music room where one note sometimes won't play, the north stairway with a steps going up and down, a statue in the schoolyard that walks around covered in blood, the art room sculpture that gets a fold in its eye late at 3:00 AM, and a dictionary in the library where the words for curse are stained red. Most prominent among these rumors is a sealed off classroom in the old school building where a student supposedly vanished several decades ago. The seventh story is said to be a secret that no one is ever to discover, should they be whisked away to the underworld by dark magic
The story in Episode 6 of the anime centers around a sealed off classroom in Sasahata North High School where students claim to have heard strange voices and growls from within. Hoping to gain back some magical power, Sadao Maou has Urushihara search for places nearby where there might be traces of supernatural energy, leading them to Chiho's high school. Though the Demon King wishes to take a closer look, Ashiya advises him not to do so during school hours due to the fact that they would be intruding either way.
Later that day at MgRonald's, Chiho explains that the mystery of the old classroom is one of "Seven Wonders" of her school, while mentioning that people have seen the shadows of demons lurking in the windows. Though Maou denies any involvement, he decides to go investigate the occurrence for himself, taking Ashiya along with him for support. After sneaking into the school at night, Chiho explains the other six wonders to Maou, but the group is stopped by Emi who berates the demons for bringing a high school girl along for their nighttime break-in. The trio tries to ditch her, only to be chased by the angry hero, who corners them in the science lab and bifurcates an anatomical model with her Sacred Sword. She then joins them in their investigation.
The group eventually reaches the sealed-off classroom, only to discover the floor littered with garbage left behind by someone who had been living there not long ago. Maou discovers a handheld game console moments before receiving a half-confession from Urushihara, who admits that he and Olba had been living in the empty room while hiding out on Earth, having largely sent the others there to retrieve the belongings he left behind. Angered by his deceit, they return home, unknowingly tailed a by a mysterious figure wearing a cloak who had come through the Gate.