Rokujouma no Shinryakusha!?

Due to his family's financial circumstances, Koutarou is forced to live in a small apartment (rokujouma) for his next three years of high school.

On the plus side, the 5,000 yen monthly rent is very affordable, but on the minus side, room 106 of the Corona Apartments is cursed.

As it turns out the ghost residing in his apartment is a girl named Sanae, and since her nightly poltergeist escapades could not drive Koutarou out, she now resorts to more physical means.

Between the haunting, a self-styled magical girl Yurika crash-lands her broom for an unneeded rescue, seeking to protect a source of abundant magic in the room.

Then a member of the "underground people", Kiriha, along with her helpers Korama and Karama, appears from a hitherto unknown cellar, declaring Koutarou's room the site of an important Earth People shrine.

Finally Princess Theiamillis with servant Ruthkhania, step through a portal into the room trying to make the "life at the room's coordinates" swear loyalty to the princess.

Landlady and classmate Shizuka certainly is not amused by the ruckus and forces everyone to peacefully resolve their issues... Koutarou's high school days quite complicated.

Note: Rokujouma means 6-tatami, which is about 10 m².