생화학 테러는 몇몇의 사람을 높은 지능과 늙지 않는 신체를 가졌지만, 자외선에 약해 밤에 돌아다니는 신인류를 탄생시킨다. 그들은 낮에 활동하는 기존의 인류를 차별하기 시작하면서, 유이와 카츠히코는 다른 옛 인류들과 함께 생존 만을 갈구할 뿐이다.

The story is set in the early 21st century with the population decimated by bio terror. Two kinds of humans now exist. One is the Nokusu who were infected with a virus but survived and consequently they carry an antibody. Most are young, healthy and have high intelligence, but they have a high sensitivity to ultraviolet rays and are active mostly during the night. The other group are the Kyurio. They survived by never having the virus. The Nokusu discriminates against the Kyurio. Tetsuhiko Okudera is a Kyurio. He was born in a poor village. He isn't happy with being a Kyurio and wishes he could be a Nokusu. Yui Ikuta is Tetsuhiko's childhood friend. She tries to revive the poor village.