1. An information processing apparatus comprising: at least one processor configured to: acquire a title character string showing a title of content; analyze the title character string and divide the title character string into a plurality of tokens; calculate, for each of the plurality of tokens, an evaluation value that is based on a character string length of the token and is weighted in accordance with a position of the token in the title character string; map, for each of the plurality of tokens, a token point, whose position is shown by a value of an ordinal number showing the position of the token in the title character string and the evaluation value, onto a coordinate plane; decide, based on coordinates of the token points mapped onto the coordinate plane, coordinates of a criterion point used as a criterion for extracting an identifier that identifies a series from the title and an extraction criterion based on the criterion point; extract token points that conform to the extraction criterion out of the token points; and generate the identifier from the character strings included in tokens associated with the token points.