I was in Tokyo looking for just this back around Thanksgiving. I walked to this street, which is away from the tourist areas and in a kitchen supply kind of neighborhood. There were 3-4 knife shops on this street and seemed to have very good selection:

https://www.google.com/maps/search/k....787506,17.26z

(near the top of the map, the cluster around "Tsubaya Cutlery World")