1. An apparatus, comprising: a memory; and a processor that: recommends a first number of times a plurality of content items to a user, receives, from a user device of the user, a second number of times positive evaluation information for the plurality of content items, wherein the positive evaluation information indicates that a content item of the plurality of content items is completely reproduced by the user device, and wherein the plurality of content items are associated with a plurality of content item IDs; generates rankings of the plurality of content items, wherein the rankings of the plurality of content items are indicated by a first list of the plurality of content item IDs in a descending order of a ratio of the first number of times the positive evaluation information is received from the user device for the content item and the second number of times the content item is recommended to the user; extracts at least two content item IDs from the first list of the plurality of content item IDs, wherein the extraction is based on the rankings of the plurality of content items and on user preference information associated with the content item, and wherein the user preference information comprises a user preference vector; sorts the extracted at least two content item IDs in a second list in an increasing order of an angle between the user preference vector and a plurality of feature vectors associated with the extracted at least two content item IDs, wherein each of the plurality of feature vectors comprises at least a feature quantity associated with the at least two content item IDs, and wherein the user preference vector is generated based on the positive evaluation information; and transmits the second list to the user device.