If you're asking how many days you should spend in Fukuoka, my answer is: it depends! If you only have time to sightsee within the city, then 3 days is a good amount.  It'll give you plenty of time to explore. If you want to take side trips and visit other cities while in the area, add a few more days to your itinerary. Fukuoka has a unique atmosphere different from any other city in Japan, so much so that it has earned the nickname "The Gateway to Asia." It's the perfect place for experiencing some of Japan's best culinary delights, seeing stunning views, and tasting traditional Japanese culture. So if you can spend more than three days here, I highly recommend it!