Based on a children's book series written by Nasu Masamoto which became a huge hit since the first book was published in 1978. The story is about a group of three six-graders who live in a fictional town Hamayamacho. All the three, Hachibe, Hakase and Mo-chan, have unique and attractive personality. The leader of this trio, Hachibe, who is active and overhasty does not like studying but enjoys sports and school lunch. Though Hakase, the brain of the trio, studies a lot and knows things, he is too shy to persist in his opinion. Easy-going Mo-chan loves to eat and thinks about food in any situation. The story unfolds the experiences of this unique trio; their everyday life including the first love, the divorce of parents, and the school life; and their adventures such as a time-trip to the Edo period and landing on a solitary island in the ocean.