William Kirk had written about Takachiho Gorge. Another similar gorge exists in Yabe. I’d like to write about what is one of the best autumn road trips in Kumamoto.
Most are probably familiar with Gorougataki (五郎ヶ滝). A few years ago, a suspension bridge (Gorougataki Tsuribashi, 五老ヶ滝吊り橋) https://tinyurl.com/bdvpadhk was built for viewing. Info and photos available here: https://8246renraku.net/archives/gorougataki.html Most might not be aware of the path following the river below the falls. It wanders along just above the water through a steep gorge for a few hundred meters, crossing from the right bank to the left, https://snaplace.jp/gorougataki/ then up a steep flight of stairs to some beautiful rice paddies. Continuing on a farm road, it eventually leads back to Tsujin Bridge (通潤橋, Tsujinkyo).
The route takes about an hour depending on how long you tarry for photography. Autumn is the best time for this. To get back to Kumamoto, take the Minamida Naidaijin-sen (南田内大臣線 https://pixta.jp/photo/25748390), a tiny road that loops south through a narrow valley with several comically tiny tunnels before plunging down a series of a dozen hairpins to meet up with Midorikawa. Very few people take that route, so one can drive leisurely, admiring the golden paddies.
After crossing Midorikawa, one will immediately notice huge tubes descending the impossibly steep cliffs forming the narrow gorge you’re now in - those feed a Chiso Corp. hydroelectric power station. Just past the station is a small parking lot of the ayu (trout) restaurant, Heikenoyu (平家の湯, https://kimukazu.me/archives/3576), whose onsen is pathetic but ayunoshioyaki (鮎の塩焼き, salted trout grilled over charcoal) is the best in Kumamoto.
After lunch, continue following the small road through some delightful autumn scenery; it eventually merges with the main road, Route 335. This will take you over Reidaikyo (霊台橋, another famous stone bridge https://tinyurl.com/43abh5p2) past the onsen, Samatanoyu (佐俣の湯 https://samatanoyu-misato.jp/) THIS is where you want to take an onsen - they have a wonderful rōtenburo. From there, it is about 45 minutes along Midorikawa until you are back in the city, near Ezuko.
The entire trip takes a full day. If you leave early, you’ll finish your short hike and be at the restaurant by lunch and home by late afternoon. Now - autumn - is the time to do it. If you have questions, please do not hesitate to post them.