Mattsu and Yamma are two boys living in Matsuyama whose favorite pastime is searching for the seven wonders of Matsuyama. One day two men turn up, and the boys are left wondering about the seven hidden gems the strangers are after. Moburi, a high school girl who acts like an older sister to them, also gets swept into the adventure. As all sorts of trouble piles up, the three must decide what future they want for their city. It is a single-episode fantasy ONA set in Matsuyama.