Fukuoka - Kumamoto left driving

Hi, I'm spending a month in Japan in March, including 9 days in Fukuoka, and I'd like to take a day trip to Kumamoto to see all the One Piece statues. It seems almost impossible to see everything in one day using public transport.

Tours are way too expensive (one ticket costs as much as two). So, my only option seems to be renting a car.

Apparently, that's quite simple with a German driver's license. I just need an official translation.

Now for my question: do you see any other options besides renting a car, and if not, how complicated did you find driving on the left, and how quickly do you get used to it? 😅 I'd rather not spend several days in Kumamoto just for the same activity.