Hiring a car in Nagasaki and returning it to Kumamoto, would the airport be a good drop off point?

We're renting a car in Nagasaki, going on a 8 day road trip and then returning the car to Kumamoto. I'm thinking that it might be a better idea to return the car to Kumamoto airport and getting the train or bus from there instead of returning the car to Kumamoto station so I can avoid driving in the city. Does anyone have any relevant experience that could help me make a decision?

by Boggins316