1. A content recommendation device, comprising: a first feature generation unit configured to generate a first feature based on information of a first type included in first content selected from content pieces by a target user in past; a second feature generation unit configured to generate a second feature based on information of a second type included in a current search request by the target user; a relational feature generation unit configured to generate a plurality of relational features that indicate a relationship between the first content and the current search request, based on the first feature and the second feature; a recommended content search unit configured to: output the plurality of relational features to the target user; receive a user input corresponding to selection of one of the plurality of relational features; and search for a first set of content pieces based on the information of the first type included in third content that is newly selected by the target user, the selected one of the plurality of relational features, and a clustering of words based on a word vector associated with the relationship between the first content and the current search request, wherein content to be recommended to the target user is selected from the first set of content pieces, wherein the third content is different from the first content; and a display device configured to present the content to be recommended to the target user.