By air plane
The nearest airports to your destination are Fukuoka Airport and Oita Airport.
Fukuoka Airport is approximately 135 minutes away from Haneda Airport and about 75 minutes from Osaka (Itami) Airport. Oita Airport is approximately 90 minutes from Haneda Airport and about 60 minutes from Osaka (Itami) Airport.
You can reach it from Fukuoka Airport by bus in about 140 minutes, and from Oita Airport, it takes approximately 47 minutes by bus.
You should go to Kokura station by using Shinkansen (bullet train). From Kokura station, you can take the JR (Japan Railways) train and will arrive at Beppu Station in approximately 80 minutes.