Matsugen   When we want noodles, we make a beeline for Matsugen because at this sleek Waikiki spot, the object of desire is soba. As at restaurants in Japan and, more recently, New York, this seemingly simple noodle takes center stage, with Shingo Shibano crafting soba for all the room to see. The restaurant even grinds its own buckwheat flour — these are fresh noodles. Eat the art as mori soba — cold noodles with only a dashi-mirinshoyu sauce, and some wasabi and sliced green onions. There is also udon, as well as izakaya dishes, from poke to top-grade meat cooked on a hot rock.  255 Beach Walk. 926-0255. 11:30- 2 p.m., 5-10 p.m. daily. JCB, MC, VS. No checks.