Saitou Yakumo is a college student. He was born with different eye colors. His red left eye gives him a special ability to see ghosts and spirits. He believes ghosts and spirits are bound to earth because of a certain 'cause' and simply eliminating that 'cause' will those spirits rest in peace. Being asked for help by Ozawa Haruka, they begin the investigation together. In volume 5 of the light novel, it is revealed that his mother, before she went missing, had never hated Yakumo. She had loved and cared for him. Takeda Shunsuke proposed to her and wanted to be Yakumo's new dad too. However that did not work out due to events caused by Yakumo's real father. When Yakumo went missing in volume 5, Haruka found Yakumo, and before Yakumo's real father could hurt Haruka in front of Yakumo, Yakumo's mother's spirit stopped it from happening and saved the both of them.