Basement.

One day, a runaway middle school girl named Nanase Seika shows up at the office of Inomata Yoichi, an underground reporter who covers the adult entertainment industry, delinquent groups, and the truth behind urban legends. At the request of Okawara Koji, a former yakuza who also provides him with information, Inomata lets Seika stay at his office, but it appears that Seika is involved in some kind of fraud...