One day, a mysterious letter 'F' starts to be written on doorplates in a condominium building. Since then, mysterious incidents consistently occur around Yukari Yamamoto, who is an ordinary female high school student living in the building.

• Jolly Roger
• Marika Ito
• Seiko Ozone
• Kosuke Endo
• Akari Yamada
• Kōji Suzuki
• Yue
• Taichi Yamada
• Hiroki Konno