With the help of his friend Kenji Matsudaira, Kōtarō Satomi moves in to room 106 at Corona House, attracted by the low, ¥5000 a month rent. The following day, while working at an archaeology site, he falls into a hole and meets a mysterious woman. He wakes up in the hospital and apparently just hit his head. At school, he joins the Knitting Club, whose only other member is Harumi Sakuraba, his upperclassman. His reason is to "do something for someone". When he comes back to his apartment, he finds Sanae Higashihongan, a ghost claiming that room 106 is her house and wanting him out but he keeps her at bay with sacred items from his grandma. They are interrupted in turn by Yurika Nijino, a magical girl who comes crashing through the window, Kiriha Kurano from underground, and Theiamillis Gre Fortorthe along with her servant, Ruthkhania Nye Pardomshiha who come out of the wall. Fighting ensues until the landlady, Shizuka Kasagi, comes in and forces them to sign a peace treaty.