To provide a portable terminal device, method, and system capable of transmitting and receiving a message to/from a person passing, while certainly keeping individual information secret.

The portable terminal device 10 acquires position specifying data, acquires a one-time ID temporarily issued by a message management server 30, performs short-range communication with a portable terminal device 20, and transmits the acquired one-time ID and the position specifying data of the portable terminal device 10 together with a message. Further, the short-range communication is performed with the portable terminal device 20, the message is received together with the one-time ID and the position specifying data transmitted by the portable terminal device 20, whether reception is performed from a prescribed range is determined on the basis of the received position specifying data and the position specifying data of the portable terminal device 10 acquired upon reception, and when determining the reception is from the prescribed range, the input of the message is received and the received message is made transmittable to the message management server 30 by the received one-time ID.