In the five years since opening, Koizumi has developed his own take on the kaiseki tradition of leisurely, multicourse meals. He has also forged an identity that is distinct from his longtime mentor, Hideki Ishikawa, whose eponymous restaurant was at this address before moving to its current location around the corner. Koizumi worked under Ishikawa for more than 12 years, and that influence is apparent in the younger chef’s clear flavors, quality ingredients and refreshing lack of formality — even though both boast well deserved Michelin stars (two for Kohaku, a full three for Ishikawa). Of these sister restaurants, it is Kohaku that has the reputation for pushing the envelope and incorporating influences from outside the established washoku (traditional Japanese cuisine) canon. But only archtraditionalists would raise an eyebrow at the idea of using caviar as a garnish or gelatin in place of kanten (gelling agent derived from seaweed).