Koikawa Shōzan [恋川笑山] (Japanese, c. 1821–1907)

Alternate names:
Insuitei 淫水亭

See: Ryūsuitei Tanekiyo 柳水亭種清 (likely the same person)

Note: Koikawa Shōzan was among the most accomplished shunga artists of the late Edo and early Meiji periods. He illustrated and wrote numerous books under various pen names. The pseudonym Insuitei (淫水亭) appears in signatures that combine all three names (Koikawa Insuitei Shōzan), and in prefaces attributed to Ryūsuitei Tanekiyo; some scholars argue the two names refer to the same person.

Public collections:
Art Institute of Chicago: https://www.artic.edu/artists/111052/koikawa-shozan
National Museum of Asian Art, Smithsonian (Pulverer Collection): https://pulverer.si.edu/node/567/title/1/0

Sources:
Lyon Collection: https://woodblockprints.org/index.php/Detail/entities/946
Nichibunken Enpon Database: https://lapis.nichibun.ac.jp/enp/Book/Shoshi/253