Each September, the riverbanks of Yamagata fill with smoke. Groups of friends, colleagues, and families set up gas burners and large pots along the Mamigasaki River and make imoni — a stew of taro root, beef, konnyaku, and green onion in a soy-based broth that is specific to the Yamagata style. The imoni-kai, the taro gathering, is not a festival in the formal sense; it is a seasonal ritual that most Yamagata residents participate in as naturally as they participate in cherry blossom viewing. The first Sunday of September brings a more organized version to Yamagata City: a pot six meters in diameter, capable of feeding thirty thousand people, operated by a team with a crane. The spectacle is considerable. But the authentic imoni-kai experience is smaller and less organized — a group of people by a river, making a specific food that defines the beginning of autumn in this prefecture. Visitors are welcome at both the festival and the informal gatherings. The stew is not complicated; its significance is contextual. Understanding that this is how Yamagata marks the end of summer changes the experience of eating it, which is perhaps the truest thing that can be said about regional food.