Lunch is a great bargain here. I would recommend eating luxury at lunch and doing budget in the evening. You can get a great quality lunch almost anywhere with salad starter, main course and drink from 1,000 yen. Pay 2,000-3,000 yen ($20-$30) and you can really eat well.
Some restaurants (often beef bowl, unagi (eel), tempura, noodles, sushi - Japanese seems to be theme here) have fixed prices throughout the day so you may as well eat these in the evening. In other (nainblky Western style?) restaurants you'll be paying 3-10 times for dinner what you would pay for lunch.
Izakaya have good lunch sets but are also good options for evening dining.
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