I used to go to Hisayama Onsen Hotel Yumeka whenever I visited Fukuoka. It is not the most impressive Onsen, but it is so convenient to go from the Eastern district of Fukuoka City, or even from Hakata. Great for a day trip.
It takes only 20 minutes from Tenjin- Fukuoka City by Kosoku (toll way). Rental car is the best option if you would like to have the freedom of deciding what time you want to go. However, you can go there by free shuttle bus from Hakata Station twice a day (11:30 and 17:30). More frequent pick-ups are available from train stations near the hotel such as Sasaguri station on JR train line.
The hotel used to be called something else but the bath house part of the hotel remains the same. It is built by the lake. There are 12 different baths and sauna in this bath house. I love the outside ones such as cypress bath and rocky bath (picture above). Chinese herb bath is a bit stingy. I am not sure about the red wine bath (sorry, only in ladies). Herb sauna is excellent! You can see all these if you scroll down the hotel homepage. The English page is only for booking.
Unless you are staying at the hotel, you check in at the bath house reception. Please take off your shoes before going up to the reception. There are free shoe lockers for you to keep your shoes while you are in the building. You can bring your own relaxing clothes and towels (small and large). I always rent the bath house clothes (Jinbei suits) but bring my own towels to save the cost.
Now, why do you need a bath sheet and a smaller thin towel (shorter than ordinary hand towel)? You need a towel to scrub yourself before going into any bath. You can use this towel to sort of cover yourself a bit, too, as you walk around the wet area. NEVER put this towel in the bath. If you do, other users would consider that the bath has been contaminated by your towel.
To the wet area, you don’t take any personal belongs with you other than shampoo or something you specifically want to use. I don’t take anything with me. There are normally plenty of good quality shampoo, conditioner, scrub gel and etc in the wash area. All the amenities are free.