Although Yamaguchi’s lunch menu is anchored to the principles of kaiseki ryōri (traditional multicourse cuisine) he isn’t averse to adapting the rules and changing things, analogous to the frequent updates tech companies send our way. However, Yamaguchi’s changes — the layer of ume (plum) jelly he tucks inside fish tempura, for example — are updates that actually work. Lunch opened with a pale pink turnip soup enlivened by a verdurous sprig of steamed seri (Japanese parsley) and accompanied by a sprinkling of pink peppercorns. The soup was a fitting and piquant amuse-bouche. As with chefs the world over, Yamaguchi is influenced by the current Nordic cooking trend. After a plate of delectable sashimi was served there was another soup: This time a clear dashi containing simmered vegetables, including daikon cooked to the exact point where the fibrous root didn’t disintegrate under the weight of the dashi it had soaked up. The result was an umami-laden tender chunk of radish. That Yamaguchi managed to coax so much from a stubborn vegetable was a visceral pleasure.