Since Japan was an island with very little iron ore, what little iron existed was used primarily for weapons rather than armor. Therefore  the blades developed along the line of slicing rather than hacking:

People are soft and squishy, so cutting them is a far more effective use of force than hacking at them. Thus was developed the king of cutting weapons, the Katana and it's companion, the Wagizashi, or short sword.

Our Katana and Wagizashi come with a semi-sharp edge which can be taken to any level of sharpness desired by someone who knows what they're doing.