Hate
The soul mask helps you to see the deepest part of anyone's soul. You look around and in all the people you only see hate.
You're supposed to see all the emotions, so why do you only see hate inside everyone?
ぞう
にく
None
It turns out you're not looking at normal people. You see so much hate because all the people you're looking at are actually just a group of zombies (ぞう).
Zombies are pretty filled with hate, so it makes sense that you'd see a bunch of hate if you used the soul mask on them.