1. A computer-readable recording medium that stores therein a computer program for supporting an operator who responds to an inquiry from a customer while referring to case data, the computer program causing a computer to perform: extracting words of the operator as speech keywords from response data on a record of contents that the operator has spoken in response to an inquiry from a customer while referring to case data; extracting response keywords from the case data corresponding to a response to the inquiry; detecting a common keyword in the speech and response keywords by matching the speech keywords with the response keywords; extracting a support keyword from the speech keywords that appears in the response data at a time near appearance of the common keyword and that does not match the response keywords; and generating auxiliary data that includes case identification information uniquely identifying the case data, a customer level indicating a knowledge level of the customer about the inquiry, and the support keyword.