Hita sits in the river basin of western Oita Prefecture, close to the border with Fukuoka. It is often sold as a "little Kyoto", which is a bit generous, but the old merchant quarter of Mameda-machi does have real texture: white-walled storehouses, narrow lanes, sake shops, and the memory of a town once ruled directly by the Tokugawa shogunate.
The reason to give Hita a full day is that the town is not only one preserved street. Kangien Academy tells the story of an unusually open Edo-period school, while the surrounding mountains hold Onta Pottery Village, where clay is still crushed by water-powered wooden hammers and fired in climbing kilns.
Hita is also a practical food-and-drink stop. The Mikuma River is known for ayu, the forests supplied the cedar for geta clogs, and Sapporo Beer Kyushu Hita Brewery makes good use of the local water. It works best as a slow day between Fukuoka, Beppu, and the Aso area rather than as a rushed tick on a rail itinerary.