Michi and her family have just moved into the Happiness House, a huge tree with all sorts of little buildings and houses built on and inside of it. Upon exploring what is to be her new bedroom, Michi finds an odd nut-like object. Before long, a strange creature, Nanami-chan, hatches out of it. The two become fast friends. Together, Michi, her family, and Nanami-chan experience all kinds of good times, as well as troubles, learning lessons and growing closer all the while.