Found all over Japan, restaurants offering tabehoudai (all-you-can-eat) courses are appreciated by foreign tourists as well as locals looking for cheap and definitely filling meal. You pay a set amount, usually starting from around 2000 Yen per person, you are allowed to eat as much as you want until your time limit runs out. The standard time limit for a tabehoudai course is usually 90 or 120 minutes. And although the term all-you-can-eat may make you think of cheap fast food chains, in Japan there is a much larger variety of restaurants offering tabehoudai. From the usual Yakiniku (Japanese BBQ) and Syabu-syabu (thin slices of meat boiled in broth) meals where you prepare your food yourself to sushi, curry, Chinese and even places with all you can eat deserts only.
You can easily spot restaurants offering tabehoudai courses by their often large signs with "食べ放題" (tabehoudai) written on them. If you rather do an internet search for all-you-can-eat places nearby these are the keywords to use:
食べ放題 - tabehoudai
飲み放題 - nomihoudai (all you can drink)
A simple google map search should show you several restaurants in your general area.