The kanji on the knife is going to be of the hisaya brand kanji which no longer exists as a brand. Tatsuo ikeda signature is actually sakai masayuki. Sometimes when blacksmiths are commissioned to create knives for a brand that isn t there own you can find there signature on the tang (nakago) but in my experience with this brand (I own about 12 of these), Tatsuo ikeda, and info I have also gotten off of keiichi, this is not the case. Keiichi at blueway does however sell 100% sakai masayuki from time to time, which are usually techahiki. Either way it has been documented by multiple member here in this forum that the hisaya brand is indeed tatsuo ikeda, and they are one hell of a quality knife. You will just have to get over the fact that you will not find the sakai masayuki kanji. I hope that this ilfo helps. Cheers.
Dylan Sexton