Probably the most overused term in culinary matters in Japan is kodawari, which implies a strict scrupulousness, usually to flavor. Attendant to the idea of kodawari is simplicity: the more unprepossessing the food, the easier it is to appreciate its adherence to basic goodness. In this regard, the purest Japanese dish may indeed by sashimi, since it is simply sliced raw fish, but the purest prepared dish is sanuki udon.
Udon are wheat noodles, which are found everywhere in Japan. Sanuki udon is from the island of Shikoku. It is udon in a clear broth made from various stock ingredients such as mushrooms, bonito and seaweed. Sanuki udon is sustenance for common people, which means it has a reputation for being very cheap, but kodawari still applies. Outside of Shikoku, sanuki udon may be expensive in accordance with the unspoken rule that once a regional dish leaves its bailiwick it becomes something of a delicacy.
The udon chain Hanamaru blithely shatters this truism by offering sanuki udon at prices that are probably lower than they are in Shikoku. The most basic item on the menu is kake udon, which is merely noodles in broth topped with green onion. A small bowl will set you back a mere ¥105. A medium bowl is ¥210 and a large one ¥315.
From there prices get more involved as you add the usual things like ontamago (half-boiled egg), wakame (seaweed), or oage (fried tofu); and there are specialties like shredded beef and curry and sesame. But the price almost never rises above 500 yen, even when you add side dishes like tempura (in my experience, not as crisp as it should be), salad, onigiri (rice balls) or croquettes.
Hanamaru is actually cheaper than buying lunch at a convenience store, which is why any outlet is usually packed with salarymen during lunch time. And almost every one of them will probably be slurping the cheapest dish, a small serving of kake udon. I’ve been told that a lot of men, under the shadow of metabolic syndrome, find this a better dietary alternative than the standard lunchtime dish of gyudon (beef bowl), but I also assume there’s an economic component to it. Still, I might be wrong. In the early evenings the outlet in Shibuya is usually packed with high school girls, who aren’t really worried about saving money but know their kodawari.