An input system, a portable terminal, a data processor, and an input method are provided that can be used to easily input a character of the type permitted to be input. The input system includes the data processor and the portable terminal. The data processor stores an input permitted character type that is a type of characters permitted to be input to a corresponding one of not less than one input box, in association with the corresponding input box. The data processor transmits to the portable terminal the input permitted character type associated with a character input enabled input box. The portable terminal sets the type of characters to be input, to the input permitted character type as received, and transmits to the data processor an input character that is of the input permitted character type as set.