Shunga, or "spring pictures," capture a vast spectrum of sensual pleasures. From the passionate reunions of great lovers, to the excitement of clandestine affairs, these erotic prints satisfy a wide range of sexual appetites. The origins of the genre trace to the Heian period (794–1185), when sexual scandals and fantasies were circulated on hand scrolls. Though these painted works entertained only the courtier class, by the Edo period (1603-1868), the genre embraced the woodblock print and rapidly spread throughout Japanese society. Reveling in the hedonistic spirit of the floating world, shunga became an integral aspect of Edo-period life. The genre not limited to the city of Edo; shunga flourished in Kyoto and Osaka as well. Until 1990s, scholars shied away from the taboo of shunga, yet advances in the field have revealed that the importance of these works exceeds mere titillation.
Eisen, Fixing Inner Obi from the series Twelve Abuna-e, c. 1825. Ronin Gallery.
While the Tokugawa Shogunate projected Confucian values and strict rules on public decorum, the private lives of Edo's citizens remained untethered. The Shogunate banned erotic books and "lascivious" materials in both the Kyoho Reforms of 1722 and the Kansei Reforms of the 1790s, but the pleasure driven lifestyle of Edo's floating world was undaunted. Nearly all ukiyo-e artists produced shunga (thought these works are often unsigned to avoid trouble with the law). Released as single-sheet prints or enpon (book containing 12 images, usually progressing from the subtly suggestive to the strikingly explicit), shunga could be purchased from book vendors or borrowed from lending libraries. The audience for these works spanned all classes and genders, generally promoting an attitude of wago, or "harmony between the sexes." Given the ubiquity of communal baths at this time, nudity was not inherently sexual, so the couples in shunga are often portrayed fully clothed with only the exaggerated genitalia exposed. These emphatic depictions portray visceral, unconscious, and unbridled desire, while the clothing allows the artist to create wonderfully colorful prints. Furthermore, the clothing and hairstyle helps to shape the narrative: who are these characters? How old are they? What is their role in society? The answer lies in the clothing and other subtle symbolism.
Utamaro, Under a Blossoming Cherry Tree from Utamakura, 1788. Ronin Gallery.
Shunga could serve an educational or inspirational purpose, but the genre did not operate in the realm of reality. These prints promoted the realm of fantasy, serving as a source of titillation and entertainment. The enjoyment of shunga was lighthearted, but these prints held a special value. They served an amuletic purpose: promising good fortune to a bride on her wedding night, protecting the warrior from death, and warding off fire. Works of shunga were often passed down through generations, shared with dear friends, or presented as fine gifts to esteemed guests. American Journalist Francis Hall's account of his welcome to a Japanese home offers an example of the special role of shunga: "He went to a drawer and brought something which he said was very valuable, and...placed in my hands three or four very obscene pictures. His wife stood close by and it was apparent from the demeanor of both that there was not a shadow of suspicion in their minds of the immodesty of the act or the pictures themselves. They had shown them as something really very choice and worth looking at and preserved them with great care (1859)." 
Eisen, Tender Embrace, 1830. Ronin Gallery.
It is important to recognize that shunga did not become impolite or taboo until the Meiji period (1868-1912). This shift resulted from the Western attitudes on sexuality that poured into Japan during the second half of the 19th century. For example, the Tokugawa shogunate presented Commodore Perry with elegant shunga paintings, among other fine gifts, upon his initial arrival in Japan in 1853. Perry's diaries reveal the immense shock of receiving such obscene imagery—the value and honor of giving the gift of shunga was lost in this diplomatic exchange. As Japan modernized following Western examples, shunga became taboo. Yet, even today, centuries-old shunga remains a treasure in some families. 
 Aki Ishigami, "Reception of Shunga in the Modern Era: From Meiji to the Pre-WWII Years" in Japan Review 26 (2013): 39
 Monta Hayakawa, "Who Were the Audiences for Shunga?" in Japan Review 26 (2013): 22.