Mia

"It's okay, they are happy, right?"

Mia is under a spell that is concentrated inside her necklace. The sadness and any negative feelings of people living in Mia's planet go to her.

As a child, Mia has always dreamed of a world where no one would suffer, it's a common dream for a child to have, but she grew up with that same desire and look after all the information she could to make it happen.
It ended up in the ears of someone who was malicious and easily manipulating various things, including people's own feelings.
It was not difficult for him to persuade Mia to accept his proposal: people would no longer suffer, in return, SHE would suffer instead of everyone. Although it seemed insane she accepted, her kindness was far greater than her logical reasoning.
She only realized the mistake shortly after accepting. Sadness and other negative emotions are part of each other's growth, and depriving them of doing so harmed more than helped at all. It did not matter what happened: deaths, illnesses, potential frustrations ... people dealt neutrally until they felt good again ... or not.
Mia is trapped in this spell indefinitely and has already settled for it. What she does not know is that people are secretly working to reverse this.