Itomori is a town located in the Gifu prefecture and is the hometown of the main heroine, Mitsuha Miyamizu.
The town was established in the year 443. The town's primary water formation, Lake Itomori, was the result of a fragment from Comet Tiamat crashing into the town 1200 years prior to the events of the film. Itomori lacks several amenities, such as cafes and hospitals. The mayor of Itomori, Mitsuha's father, even noted that she would have to be sent out to the city to get examined by a doctor at a hospital, presumably due to Itomori's lack of such facilities.
The town surrounds the crater of what is believed to be the fragment. Most of the buildings in the area a 2-storey family houses. The town is accessible by train and road. The area itself is mostly rural, with farmland and gardens covering the space between the roads and houses. The town is powered through a single substation.
There is an apparently mystical connection between Itomori and Comet Tiamat, one stretching for potentially thousands of years. As stated in the film, Tiamat possesses an orbital period of 1200 years, and the comet has hit the town at least twice (once during the formation of Lake Itomori, another during the film in 2013). It is also implied, due to the size and structure of Goshintai, that such a site was formed through another fragment of Tiamat crashing to the ground below. Taki hypothesizes to Hitoha Miyamizu that the Miyamizu line's body-swapping ability may be inextricably linked to the possible prevention of such disasters.
Itomori was disestablished following the Itomori Accident of 2013. In one timeline 500 people died in the incident, and in the final timeline all of its residents survived with only 104 people injured, but it was implied that the town was largely abandoned and its residents moved to Tokyo or elsewhere. Indeed, many of the primary residents of Itomori migrate to Tokyo following its destruction in the revised timeline, leaving the once-beautiful town desolate and relatively barren. While many characters in the film are shown living their lives in Tokyo (Mitsuha, Yotsuha, Sayaka, Tessie, and Ms. Yukino), it is unknown where many of the unnamed former residents of Itomori have relocated to.