Japanese curry is very different from Indian or Thai versions because it is usually much thicker and quite a bit sweeter too. It is total comfort food over there and super popular across the whole country with unique styles you absolutely need to check out. I really think you should try it if you have the chance.
Katsu Curry At A Specialized Shop

This is the one that a lot of people probably know where a juicy fried pork or chicken cutlet sits right on top of a big pile of rice and curry sauce. It is a very filling meal and for a really authentic taste you can look for shops like Tonkatsu Maisen in Tokyo that specialize in fried cutlets because they just do them so right.
Basic Curry Rice At CoCo Ichibanya

Sometimes you just want the classic plain curry over rice with nothing fancy added and that is where the famous chain CoCo Ichibanya comes into play because they have locations everywhere in Japan. What is fun is that you can choose your spice level from mild to super hot and also decide exactly how much rice you want which makes it a really personalized plate of food that is quite affordable too.
Curry Udon Noodles

If you are not feeling like having rice again then curry udon is a great choice because they take that same thick curry sauce and use it to make a warm broth for thick chewy noodles. Lots of traditional udon restaurants serve this dish but the noodle chain Hanamaru Udon has a really solid version that is easy to find when you are out exploring.
Soup Curry In Hokkaido

Now this style comes specifically from Hokkaido up north and it is very different because it is a thin spicy soup filled with big chunks of tender vegetables and usually a whole chicken leg. It is a really nice change and for a great bowl you should try to find a shop called Soup Curry Garaku which started in Sapporo but has other locations now.
Curry Bread From A Bakery

You have to try this because it is basically a slightly sweet dough filled with thick curry sauce that is then covered in breadcrumbs and deep-fried until it is crispy golden brown on the outside. It is the ultimate snack that you can grab at almost any bakery in Japan like Andersen Bakery and it is perfect for when you need a quick bit to eat.
Dry Curry Rice

This style is more like fried rice where they mix the rice together with ground meat and veggies and lots of delicious curry spices so it is not saucer like the others we talked about. It has a slightly different flavor profile that some people really prefer, and you can usually find it on the menu at many older Japanese-style cafes or “kissaten” places.
Kanazawa Curry

This regional style from Kanazawa city is known for being extremely thick and dark and they always serve it with a pile of shredded cabbage right on the same plate. The chain Go! Go! Curry has made this style famous all over the country and it is really hearty and filling especially with that distinctive dark sauce flavor.
Instant Home Curry

Okay so this point is not at a restaurant but you should buy the instant curry roux boxes at a grocery store in Japan because they are so easy to make at home. It is what most families eat there and brands like Vermont Curry or Java Curry are classic choices that make for a really simple and nice souvenir to take back with you.
Convenience Store Curry

You are probably going to visit a convenience store or ‘konbini’ like 7-Eleven or Lawson anyway so grab one of their bento box curries because they are surprisingly good for the low price. They will even heat it up for you right there at the counter so it is hot and ready to eat immediately which is super convenient when you are busy traveling around.
Beef Curry At Gyudon Chains

Lastly, for a quick and budget-friendly meal you can pop into a beef bowl chain like Yoshinoya or Sukiya and order their simple beef curry. It is not overly fancy but it is incredibly consistent and reliable when you want a warm meal without waiting or spending too much money.