Read up on Samurai and Bushido a bit.
Question: Do you know ANYTHING about Bushido at all?
Tantô class is rather specific, as most knives (for battle) are refered to as tantôs. A tanto is 6"-12" in length and is used primarily as a stabbing weapon. It was used for hari-kari (ritual suicide) or as a hidden weapon. They were used for suicide, stealth, and for a backup weapon.
A Katana was the eastern version of the longsword, it was NOT "a big long-reach weapon" as you put it. The Daito is used to refer to most Japanesse battle swords, as they were the primary weapon of soldiers. The two most common in this category are the Katana and Tachi. The Katana is the standard sword that soldiers used, whereas the Tachi, while slightly larger and mored curved, was used by calvary more often. The ôdachi was also, but rarely (despite the common useage in manga and anime), used by soldiers. The ôdachi, which means large tachi, had a blunt edge, but a sharp tip. It was used mostly to knock off people from horseback and to cripple the horses legs. The ôdachi, as it was a very large blade (commonly 3 shaku), required a large amount of skill to wield the blade effectively. They were also rare because the naginata and nagimata were far more effective at that role on the battle field.
Bushido is the samurai's code. I will not bore you with the specifics, just look into it.
Here is my advice: Make the Tanto and the Katana strong and weak against various foes. Tanto would be strong against archers and the ninja you face in the beginning, but the Katanna would be stronger against the horsemen and the bosses. Also, do NOT make the bosses so lame. Hitting one in the back is a disshonorable deed in Bushido. Ninja, however, do not follow Bushido. Is the main character a Samurai or a Ninja? Make up your mind. I suggest that you make the Boss battles cinematic sequences where you have to hit certain buttons at the right time. Your art style is great so you should use that more often instead of making so much of it lower-quality game graphics.