Especially in Osaka and Hiroshima city. I don't want a luxury restaurant. Just simple cafe is preferrable.

mmmmm in Japan no such cafe in Europe exists here.
You may pay for sandwiches and soft drinks at coffee shops with $10 so.

If you'd go white table cross restaurants for dinner of French or Italian, it costs around $50 to $100 without any drinks everywhere in Japan.

In Tokyo I'd say 1,000 yen for lunch, and 1,000 - 2,000 for dinner. I'm not familiar with Osaka or Hiroshima but I expect the prices to be about the same.

Not to sure about Osaka but check out http://www.gethiroshima.com/ . They have a good list of reviews on restaurants in Hiroshima.

I've never been to Europe so I can't compare but what I would call a cafe in Japan is a kissaten and it's not exactly for eating meals, more for having drinks and some food with the beverages. Here's a menu in Osaka so you can see some prices.. but I don't know if you can read so I'll translate a few items.

http://www.originalcoffee.net/cafeopen10.html
special blend coffee 400
orange juice 500
milk 400
ice tea 400
coke 400
pancakes 450
ham sandwich 600
beef curry 600
omelette rice 700
italian spaghetti 600
tonkatsu 800