Where in Japan will you be staying and which Suntory distillery will you visit? If you are in a larger centre then you can probably sample a range of styles at a local whisky bar or at a decent restaurant. You might want to try your hand at some of the shochu (distilled spirits from rice, potato, sweet potato, etc.) or nihonshu (rice wine) while you are there.
Narita Airport duty-free shops sell both Yamazaki 12 and Hibiki 17 (but usually the chill-filtered one), and those are a good place to start. The latter is particularly full-bodied for a blend and will serve you well. At 7000 yen/bottle (about $70) your wallet will take a hit. You will find it to your liking if you enjoy bourbon. The non-chill-filtered costs 1000 yen more and is worth it.
Most of the Hakushu (by Suntory) whiskies I tried were fairly light and refreshing; I quite enjoyed them all of them very much, though less that some other brands.
Suntory recently came out with a vintage malt series for customers with fatter wallets and an adventurous spirit. The flavours (and prices) between the vintages vary a lot, so I would recommend sampling a range and then settling on one that you like. My personal favourites were the Yamazaki Vintage 1982 and the 1989. You can expect to pay over 10,000 yen per bottle, though the distillery might sell them for less.
Yoichi is made by Nikka, so you won't find it on the tour. The 10 is easy to find at retail outlets and usually costs about 4000 yen. It is a great buy, but if you lay your eyes upon the 10 c.s. or the 15 you would do well to spend the extra money.
One thing you will notice is that hard alcohol prices are very low there compared with Canada due to low taxation of spirits. As a result, you'll find many a bargain on scotch and bourbon. The better shopes in Tokyo and Osaka carry a mind-boggling range of whiskies, including several bourbons that will never make it to Canadian shelves in the near future.
Good luck and have a great trip.