When choosing a Japanese kitchen knife here's a few things to consider:
Which Knife type?
all-rounder: the Gyuto or Santoku - the standard domestic knife in Japan.Get one of these if you're starting out. Technically, the Santoku has a broader blade, while the gyuto is more slender, and based on a western chef's knife.
veg knife: Nakiri - good for meat as well. Usuba - this one's a bit special, it's single bevelled for traditional Japanese veg prep, wafer thin sheets of daikon radish, that sort of thing.
small knife: Petty
raw fish: Yanagiba (single bevelled)
filleting fish: Deba, Mioroshi, Ajikiri (all single bevelled. Deba is the largest and most substantial, Ajikiri the smallest (named after the aji fish, a kind of mackerel) while Mioroshi is an interesting take on the Deba, with a touch of Gyuto thrown in.
For beginners, think about the stainless steel Tetsuhiro range - they won't blow you away, but are a great introduction to Japanese knives. Beyond that, do you want a more traditional Japanese feel (Masashi's knives and the Carbon range have Japanese style handles) or a heavier, more substantial Western feel - in which case go for the Nashi or Western range.
White Paper Steel is the easiest to sharpen but Blue Paper Steel holds its edge longer while SLD and VG-10 are hard wearing and semi rust proof (Tadafusa Kobo, Masashi, Shigeki)
Masashi, needless to say, are the nicest, but the Niwaki Carbon and Niwaki Nashi hit a sweet spot of quality and value, giving you triple layered steel at an affordable price.