When I went, Kumamoto Castle collapsed due to the earthquake, and part of it was being repaired. I couldn't visit the Kumamoto Castle, which was damaged and closed due to the earthquake. Unfortunately, I can only overlook the outside. But you can still watch it close, and after all, there are many famous Kumamoto and souvenirs!
For a day trip in Kumamoto, you can take the tram to Kumamoto Castle Station and walk along the moat. You can see the building walls destroyed by the 2016 earthquake. Large blocks of rocks are falling down. It looks good. Poor~ I can walk across a small bridge to the Josai-en to sell some snacks~ Keep going forward and you can go uphill. Seeing Kumamoto Castle, the building has been seriously damaged and has been undergoing maintenance. I hope it can be repaired soon. See the style of Kumamoto Castle~
This is a lovely castle and museum. Enjoy the climb to the top as there are many steps. It is worth it.
There aren't many well-preserved historical Japanese castles on the island of Kyushu, but Kumamoto has a good one. After you've toured the castle, head over to Suizen-ji garden, one of the most famous traditional gardens in the country. (No kidding, it's a national landmark - but why is it so far out of the way down in Kyushu? Good question.)
Kumamoto castle was designed by lord kiyomasa kato.