Well, take a Hello Kitty Shinkansen from Osaka to Hakata, and then visit Kumamoto! It’s just half an hour Shikan-sen ride between Hakata and Kumamoto!

https://edition.cnn.com/…/hello-kitty-shinkansen…/index.html

On the website regarding this bullet train (though it is only in Japanese. Sorry!), JR says, “Train operation days after October are TBA” in small letters!
http://www.jr-hellokittyshinkansen.jp/train/

Here is another article on the Hello Kitty bullet train!

https://www.cnet.com/roadshow/news/2018-hello-kitty-bullet-train-sanrio-shinkansen/