Takeuchi Masami has been kicked out of his house by his uncle after the death of his father. The meager allowance his uncle sends him is hardly enough to find a decent place to live, so at the beginning of the story we find him shacking up at his school, while his cute classmate Kagome Nishino is trying to help him find an apartment.
As it turns out, she has just found the perfect one, and whisks Takeuchi to a bare, unfurnished place and talks him into moving in right away—in fact, spending that same night there, alone, and without even a futon to lie on. It turns out that she has an ulterior motive: she is heavily into the supernatural, having just formed a "paranormal research club" at their school, and the reason the apartment is so cheap is because it is said to be haunted, something she conveniently does not mention to Takeuchi, who almost dies of fright that night when all sorts of spooky things begin to happen all around him.