Okay so I remember VERY little about this manga because I wasn't that far into it yet and I read it a long time ago.
The MC was a female who woke up in another place/world where the only things around were buildings. Her and the other characters had to stay on the rooftops while getting chased by murderers with masks on. I think looking at the back of the masks made the person insane. The MC also might have been looking for her brother.
Okay so I remember VERY little about this manga because I wasn't that far into it yet and I read it a long time ago.
The MC was a female who woke up in another place/world where the only things around were buildings. Her and the other characters had to stay on the rooftops while getting chased by murderers with masks on. I think looking at the back of the masks made the person insane. The MC also might have been looking for her brother.