One of the Japanese restaurant I'd frequent is Gaijin Lunch Bar, located on Lt Bourke St, Melbourne. I stumbled upon this place while strolling the streets with a friend on a summer afternoon few months ago and decided to walk in for cheap cider (thumbs up for happy hour!). I returned for food few days later, ordering a soft shell crab meal I promised myself to order next time I was there.
It's very casual and relaxing, a place you would go for cheap eats and good service. The downsides would be cash only payments and food served in disposable bowls however you do get an affordable lunch, reasonably priced alcohol and the friendly cashier remembering your name - I'd recommend Gaijin for those short of money, like us university students! Be sure to grab a seat on the sofa looking out onto the street and immerse yourself in the world of Japanese cuisine, knowing it won't break your bank account.