The system in one embodiment operates while automatically switching among three processes including an absent-at-home guard process, an at-home guard process, and a non-guard process according to the positional relationship between the movable localizer and the internal guard surfaces/the external guard surface. When an actuator (such as a speaker and a white smoke generating unit) is integrated into the localizer, the localizer located at an intruder generates alarm sound or white smoke in the absent-at-home guard process. When the intruder moves inside the house, the localizer generating the alarm sound and the localizer generating the white smoke change following the intruder. The actuator is controlled such that an intruder is discouraged to approach the internal guard surface or such that a house member inside the internal guard surface can evacuate in a direction departing from the intruder in the at-home guard process.