The 'detox water' outside should give you a hint as to what makes Hana wa Saku tick: the owners are on a self-proclaimed mission to deliver 'healthy udon that makes you genki'. In practice, that means thick, chewy al dente noodles (made the day before as to make them even more springy), served up with a dazzling array of uber-organic vegetables (locally sourced, pesticide & additive-free, the works) or topped with premium wagyu beef. They even do salads. Their vision seems to be working, as their noodles have won them second place in a national udon competition.
Their most popular option is the Gokujo Niku Udon ('The Best Meat Udon'), an ambitiously-named concoction topped with sukiyaki-style slices of premium A5 kuroge wagyu beef and a perfect egg yolk, plus some condiments. At ¥1,600 for a standard portion, it's hardly a cheap eat, but quality-wise, you're getting proper bang for your buck. The smooth noodles, well-seasoned beef and runny yolk make for a rather upscale but immaculate rendition of comfort food.
Although you could spend a good chunk of time and money swooning over the above, their (cheaper) other options are also more than worth a gander. The bukkake udon with four-vegetable kakiage (¥900) in particular will make you reconsider kakiage: the massive concoction is filled with sticks of expertly tempura'd seasonal vegetables which are still properly cooked through, yet stay firm enough to stand upright. It's a world away from the often gloopy, oily messiness served at lesser udon places.
The Nakano curry udon (¥950), on the other hand, surprises with its less-conventional toppings, which included mochi tempura, minced umeboshi and shiso leaf, besides more traditional ingredients such as sweet potato, carrot and pumpkin. The curry is more of a sauce than a soup, and although that does make it heavy to stir around, it's not cloying, and the entire thing still feels healthy, with the noodles doing all the heavy lifting. Even if you're not a regular curry udon fan, this bowl might be able to win you over.
Hana wa Saku has been in business since 2013, and considering the quality, we're slightly surprised that the queues here are quite manageable. They do get crowded, especially at weekends, but it's nothing compared to some of the legendary lines at other noodle joints. Get there before that changes.