The story of Twilight Syndrome: Saikai focuses on four Japanese teenagers: Yuri, her sister Masa, and their friends Atsushi and Aya. It all begins when the youngsters hear rumors about spirits contained in the school building. At night, Yuri and her friends go into the school and play a spirit-summoning game. Suddenly, real ghosts appear and scare the teenagers away. The next day, Yuri is almost ready to believe it was all a dream... but naturally it wasn't. The dark secrets of the lost souls are going to be revealed only to those which possess a special sense - the Twilight Syndrome..