Invaders of the Rokujouma!?

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.

Corona House's landlady, Shizuka, imposes the Corona Convention on the lot, which causes the invaders to rethink their strategies. Meanwhile, Koutarou participates in the Knitting Society, where its president, Sakuraba Harumi and Koutarou spend their time, away from troubles, but then there's word that four new students will be transferring into his school...

The lot continue to fight over the room, and eventually decide to use the inter-club obstacle course marathon as their next battleground. Koutarou and Harumi enter as part of the Knitting Society, along with Sanae. Theia and Kiriha get their underlings and make their preparations.