Yuri Honjo.

At the beginning of the story, Yuri is a young woman of slender build. She has long black hair (brown on some covers) and light brown eyes. She wears a blue and white sailor-style school uniform with a school bag.

Yuri has a cheerful and friendly personality, making her form friendships on her journey. She has a complex love for her brother "Rika Honjo," whom she resembles in certain traits; her character develops throughout the chapters, and she bases her decisions on common sense. She is a flexible person. She can kill the masks, but her kind nature has caused her problems.

A 16-year-old female student with a cheerful personality. She arrives in an inexplicable world where a man in a "mask" kills another before her eyes. During the story, she learns combat skills. She has a firm conviction to live and to find her brother in this strange world. She meets a cruel young woman named Mayuko Nise, and over time a friendship develops, built on trust and goodwill. They form a team to take the "helicopter," their only hope of escaping this world.

A world full of skyscrapers from which no one can descend, inhabited by humans with masks called "Angels" or "Masked Ones" who will kill any unmasked human in front of them. There are four types of masks: smiling, angry, serious, and mouthless. The smiling ones can attack unmasked humans and incite them to suicide; they will fight without hesitation. The angry ones don't fight without reason; they are strong and intelligent. The serious ones don't seek to fight and will only provide resources to the unmasked. The mouthless masks can transform you into a near-god user, making you stronger and developing supernatural powers.