The place is called Saizeriya, and it's a chain of Italian style restaurants that are quick, inexpensive and also family friendly!
The store logo looks like this, if you're out and about looking for it!
Firstly I have to say that I love the culture of Japanese family restaurants. There's a few different chains - not just Saizeriya for Italian style cuisine - where you can get a good feed for a price that won't break the budget. Especially since we have a toddler right now, being able to eat quickly, cost effectively and somewhere that also caters to kids is incredibly helpful.
There's a few good options here for around the 400 yen mark! Personally I like tomato based pasta sauces rather than creamy sauces, so I tend to opt for the meat sauce pasta. Not a bad deal at all for 399 yen! You can get a soft boiled egg for it too, if that interests you - but it's not really my cup of tea so I just get it as it is.
I actually had to look up what Doria was the first time I saw it on a menu, since I'd never had it before or even heard of it! The best definition I found comes from here which describes Doria as "a rice and butter based dish which typically has chicken or prawns, and some vegetables mixed in, with a creamy white sauce (maybe cheese) on top." The one here served with meat sauce is only 299 yen!
A sampling of what is on offer on their pizza menu - the triple buffalo mozzarella pizza is really good, and for 499 yen you can't go wrong!
Hamburger steaks are something I've really come to love since living in Japan. It's something we make at home too (I use this recipe here which has always turned out great, if you want to try to make it yourself!) but sometimes you might just be craving it when you're out. I love that you can get a full meal with some meat, veggies and potato wedges for around that magic 500 yen mark. You'll see below there is one option that is 599 yen, but it's got extra meat like sausage and bacon too.
I haven't tried these myself but looking at the menu now I think I might give them a try next time I go here. The chicken with the veggie salsa sounds good to me!
If you have some extra yen burning a hole in your pocket, there's a bunch of dessert options too. The thing I like about Japanese desserts is that the portions are just right to get your fix from a sweet treat, but not enough to make you feel like you've just ingested a weeks worth of your sugar intake.
There's more menu options too - sides, soups, salads, and drinks for example - but if you're just trying to go the one coin route then hopefully some of those choices will take your fancy. With drinks as well, you'll find water available for free (if you're wanting soft drink or juice then that's on you - but Saizeriya does do a free refill drink deal which can be handy if you're craving something other than H20).