The main character's mundane daily life is turned upside down when a certain woman appears in his life. One day, a magic circle suddenly appears in the main character's room, out of which materializes an injured woman holding a sword and clothed in knight's armor. This woman's name is "Cattleya". She claims to have been transported from another world. Until she finds a way to return to her own world, she will be an unexpected guest in the main character's home... Will Cattleya be able to safely return to her own world? Or could her fate take another turn...