The swords depicted in the anime and manga series "Demon Slayer: Kimetsu no Yaiba" are referred to as "Nichirin Blades" within the story. While these blades bear some resemblance to katanas, they have unique properties and features specific to the series.

Nichirin Blades in the Demon Slayer universe are said to be forged from a special ore called "Sun Steel" and infused with different colors that represent the user's unique abilities. Each blade possesses a distinct pattern and ability associated with its color. These swords are designed specifically to combat demons, and their unique properties play a crucial role in the story.

In terms of appearance, Nichirin Blades in the series generally resemble traditional Japanese swords like katanas. They have a curved blade, a single edge, and a circular or squared guard. However, their unique abilities and the fantastical elements associated with them differentiate them from conventional katanas.

It's important to note that the world of "Demon Slayer: Kimetsu no Yaiba" is fictional, and the swords depicted in the series are artistic creations within that fictional universe.