1. An information processing apparatus comprising: a receiving unit that receives a target character string; a determining unit that determines whether or not a sentiment character string is included in the character string received by the receiving unit, based on a memory that stores a sentiment character string, which is a character string representing a sentiment, and a label representing the sentiment, the sentiment character string and the label being associated with each other; a first assigning unit that assigns a label corresponding to a sentiment character string to the character string in a case where the determining unit has determined that the sentiment character string is included in the character string, and that assigns a plurality of label stored in the memory to the character string in a case where the determining unit has determined that no sentiment character string is included in the character string; an extracting unit that extracts a word from the character string; a second assigning unit that assigns to the word extracted by the extracting unit a label which has been assigned to the character string that includes the word; a modeling unit that performs supervised topic modeling for the character string, based on the character string to which the label has been assigned by the second assigning unit, as supervisory information; and an output unit that outputs a result of a process by the modeling unit.