I really enjoyed the sushi at Hakata Toyoichi at Bayside Place in Fukuoka. They are located right by Hakata Tower and the Hakata Bay International Terminal. Here is a link to the Hakata Toyoichi website.
As with any restaurant that isn't 100% gluten-free there is always the chance of cross-contamination. I had my Japanese speaking husband with me and most of the nigiri sushi was ok for me to eat, and it was very delicious.
In the photo the nigiri sushi is mine, the two Gunkan Maki sushi in the top right-hand corner are my husbands and are not gluten-free.
It is a large place. You are shown to a table and then get up and choose your sushi at a large buffet area. The wait staff then come round your table and tally your bill.
You can also order different foods off a menu such as grilled seafood and you'll get a small grill brought to your table. I can't speak to the cross-contamination on the grill from gluten soya sauce as we didn't chance it.
I would go again next time I'm in Fukuoka. It was very tasty.
The surrounding area is nice. The Hakata Port Tower is on the other side of the building. It was designed by the same fellow who built Tokyo Tower, Naito Tachu. It is 100 metres tall and there is an observatory floor at 70 metres. It is free. You get a nice view of Fukuoka and the port. Closed on Wednesdays. Hours at the time of this blog are 10:00 to 20:00 with the last entry at 19:40.
If you are a fan of Terrace House, then you should know one of the episodes was filmed by the harbour.
There are other restaurants and shops in the area, including a small aquarium.
I will definitely go again if I find myself in the area.
Note: These are my personal experiences and opinions. Always seek out a medical opinion for medical concerns. Not sponsored. If sponsored I will always say so at the top of the post.