Kōka (弘化) was a Japanese era name (年号, nengō, literally "year name") after Tenpō and before Kaei.
This period spanned the years from December 1844 through February 1848.
[1] The reigning emperors were Ninkō-tennō (仁孝天皇) and Kōmei-tennō (孝明天皇).
The nengo was not changed concurrent with the accession of Emperor Komei; instead, the Kōka era was retained until about a year after the new emperor was enthroned.
[2] During these years, Hiroshige began making a series of prints showing beautiful women in contexts of famous places.