Aradama and O-katana

They appeared last time, but what are aradama?

Are they living things?

I, Kohagura Ellen, shall explain!

The O-katana which we Toji wield are made from sacred steel, Tamahagane, but...

When Tamagahane is being refined, impurities called Noro are left behind.

Noro can easily accumulate and meld together...

...and transform into creatures that induce calamity, the aradama!

I see...!

In summary, it's like how eraser dust clumps together, right?

Nice conclusion!

So they're dirt. I get it!

She's treating a threat to humanity like an eraser!