After Koutarou Satomi's father is unexpectedly transferred for work, the first-year high school student must find an affordable place to live on his own. He eagerly accepts the chance to rent Room 106 at Corona House for just five thousand yen a month. Things start smoothly, but Koutarou's life takes a strange turn when he discovers a mysterious cave while working a part-time job.
The next evening, a series of seemingly mythical figures show up at his door, each insisting they have the rights to the student's apartment. These invaders include Sanae Higashihongan, a ghost who claims the room is haunted, magical girl Yurika, alien princess Theiamillis Gre Fortorthe, and Kiriha Kurano, a direct heir of the Earth People. More importantly, each of the four girls needs Koutarou's apartment for her own reasons and refuses to back down without a struggle.
Rokujouma no Shinryakusha!? is a comedic free-for-all over a six-tatami mat room, blending supernatural beings, romantic high school antics, and a surprisingly friendly landlady.