This study addressed the automatic classification of Japanese manga held by public libraries. Holdings of 4,681 public libraries and similar facilities were investigated, and 29,795 manga titles were identified. Hierarchical clustering was applied to 631 titles that were each held by more than one hundred libraries. Five clusters were identified in the upper hierarchy. Principal coordinate analysis and a manual examination of individual titles were performed to identify the common characteristics of the works in each cluster. The results suggest that the proposed method offers a novel approach to large-scale classification of manga titles.