Hiroshi is a boy, a bit lazy in school and in his daily tasks. One day, fighting against his bullies classmates, Hiroshi accidentally fell over a frog who was jumping through Nerima, Tokyo Shakujii Park. Due to this incident, Pyonkichi, the frog, became a "flat frog" and his image and spirit get impregnated on Hiroshi's t-shirt. Due to this shirt being the only one that Hiroshi has kept in good shape, he is forced to wear it everyday, interacting with Pyonkichi and becoming friends. Pyonkichi has total control over the t-shirt, being able to move it at will, despite what Hiroshi may want.