Tsuhi no hinagata (Patterns of loving couples)

This set is considered one of Hokusai's masterpieces. Richard Lane notes in Hokusai Life and Work (New York: E. P. Dutton, 1989) that there are at least two versions, printed from different blocks. There are also an aiban size later edition and a Meiji facsimile edition, which comprising five plates from this set and seven from another title, indicative of the popularity of this set.
For another set, which is considered the first edition, see Hayashi Yoshikazu and Richard Lane, Hokusai, Tsuhi no hinagata, vol. 13 of Teihon ukiyo-e shunga meihin shusei (The complete ukiyo-e shunga) (Tokyo: Kawade Shobo Shinsha, 1997), pls. 1-12.