Nowhere is a place outside the universe where all multiversal anomalies are sent to live in peace and harmony. Among those anomalies are the Demons.

To identify Demons and "humans" in Nowhere you need to know the following:

If it has any physical alterations (tail, fangs, claws or animal legs) it may be a furry. But if they have horns and/or colored eyes it is a demon.

To identify different ranks of demons:

If it only has a tail it is a low-level Demon. It can think straight and it's a nice Demon.

If it has claws, fangs and/or horns it is a mid-level Demon. These demons can present aggressive attitudes when presented with a problem, something that can cause collateral damage around them.

And if they have bright blue eyes they are high level Demons. These are very dangerous and can kill people without thinking. It is advisable to stay away from these.