Long ago, during the Edo era, the sankin-kōtai (参勤交代) system required that either the local lord or his wife be present in Edo at all times - y’know, just in case. The Higo (Kumamoto) lords made this trip by travelling overland to Bunzen (now Oita) and catching a boat, kind of a long trip overland, and the route still exists. It passes by a spot known as Sanrigi (三里木) - “trees at the third ri.”.
Here, the matter of “ri” 「里」 becomes a bit complicated. It is a unit of distance, but in China, the kanji indicates 500 meters, while in Korea, it’s about 400 meters, and in Japan, the same kanji indicates a distance of 3.9km, meaning that Sanrigi is about 11.7 kilometers from the castle - a good place to take a snack break. Currently, the area is popular as the gateway to the Hikarinomori shopping mall.
The reason I mention this is that JR and Kumamoto Prefecture are looking into rail service to the airport, and three stations on the Bizen line are being considered: Sanrigi, Haramizu, and Ozu. The candidate Sanrigi station would include a stop at the KK Wing area. JR is willing to pump money into this. Access to the airport is easy for me as I live downtown and can bus, but for those in that burgeoning area of Kumamoto, access is currently nil. Kumanichi has data at the link. - William