No, traditionally, only one side of a katana's blade is sharpened, while the other side remains relatively flat. The sharpened edge of a katana is called the "ha," and it is located on the outwardly curved side of the blade, known as the "omote." This side of the blade is used for cutting and slicing.

The other side of the blade, called the "mune" or "uragachi," is typically flat or only slightly beveled. It does not have a sharpened edge and is not intended for cutting. The mune provides structural support to the blade and helps to distribute forces during cutting motions.

This asymmetric design with a single sharpened edge is one of the distinguishing characteristics of the katana. It allows for precise cutting and enhances the overall cutting performance of the sword. The single-edged blade design also helps to reduce the overall weight of the sword, making it easier to wield and control.

It's worth noting that there are other types of Japanese swords, such as the wakizashi and tanto, which can also have a single sharpened edge. However, there are some variations and exceptions depending on specific sword styles and historical periods.