Death.
People would assume that once they experience death, having to experience it for the second time is like a simple thing passing by that can be compared to some seasonal rain with clouds and thunders.
But that was not the case for Neirin. Everything right now looked too sinister compared to her first death. The place, the people, and her state of being. Back then, It wasn't uncomfortable like this.
In her first death, she was with Vincent. Vincent was crying for her. Those tears he shed were a form of comfort that made her realize that even death can be somehow peaceful. Even after she died right then, she would have no regrets.
There was anxiety, despair, guilt, and disbelief, creeping inside of her that after all that had happened, even from her decision to take a different path from her previous life, she could not escape death.