The apartment house that the father built Shirahase Mio, "Castle Kagome Sou", is to live placidly and have fun, but only for people with a strong personality. The grandfather of Mio likes to travel, so she has to take over the apartments, collect the sales and arrange things so that tenants feel good, but it is not an easy task for a group of sixth graders.

Includes oneshot: Hitoshi Kou yu Rapsody (仁向湯ラプソディ)