When Koutarou Satomi's father is unexpectedly moved for work, the first-year high school student is forced to find an inexpensive place to live on his own. Naturally, he leaps at the chance to move into Corona House's Room 106 for only 5,000 yen per month. But, while everything appears to be going well at first, Koutarou quickly discovers that he has gotten far more than he bargained for after stumbling onto a mystery cave while doing his part-time job.