1. An information processing apparatus comprising a processor, wherein the processor executes a process including: an input by key operation, where the input is in a first character format or a second character format, the second character format being different from the first character format; determining whether an input inputted by key operation is a special character or a special word of the second character format; while a character string candidate for the input in the first character format is presented and when, by determining that the input is the special character or the special word of the second character format, the input is in the second character format, presenting character string candidates in the first character format and the second character format; while character string candidates in the first character format and the second character format are presented and when, by determining that the input is the special character or the special word of the second character format, the input is in the second character format, presenting the character string candidate in the second character format; and while the character string candidate in the second character format is presented and when an input in a character format other than the second character format is inputted, presenting the character string candidate in the first character format.