After giving a lecture at his hometown, Yonezawashima, the old mathematician Uchida Yutaka wandered to his alma mater, and met Sekiguchi Hajime, a fifth grader who enjoys playing with numbers. He was trying to unravel the world using his own equations. The movement of clouds, the branching of a tree, the veins of a dragonfly, license plate numbers, deciding class representatives.... Hajime wants to explain the unknown world using mathematics. If you read it you will grow to like maths a little. The way you look at the world will change.