1. An information processing apparatus comprising: a setting unit that sets a search character string; a searching unit that searches information including the set search character string; and a determining unit that extracts a co-occurrence character string candidate group other than partial character strings appearing as only a part of other partial character strings, among all partial character strings appearing in a plurality of pieces of the information obtained as a search result, and determines a co-occurrence character string from the co-occurrence character string candidate group, on the basis of the extracted co-occurrence character string candidate group and kinds of characters used in characters before and after the co-occurrence character string candidate group.