In Japan, oshidori (Mandarin ducks: 鴛鴦 Aix galericulata) are a symbol of marital happiness and fidelity. In fact, as legend has it, the devotion between a married pair of ducks runs so deep that should one of them die, the other will not survive. Married (human) couples in loving relationships are referred to as oshidori-fûfu ("a couple of lovebirds": おしどり夫婦). Separate kanji characters are used in Japanese for female (鴦) and male (鴛) ducks. In kabuki dance, actors sometimes performed as oshidori no seirei (spirits of Mandarin ducks: 鴛鴦の精霊 also おし鳥せい霊 or おし鳥の精霊), as is the case with Sadahiro's diptych.
The plot of the play Keisei imose no oshidori (A courtesan play: Husband and wife mandarin ducks: けいせい妹背鶫) is unknown to us. In Sadahiro's diptych, the two actors Nakayama Nanshi II and Arashi Sangorô III are on the bank of a river or pond, performing a dance while dressed in oshidori costumes.
This design is one of Sadahiro's most charming visualizations of kabuki dance and is a decidedly difficult-to-find diptych.
References: HOP, p. 22, fig. 9; Museum of Fine Arts, Boston (11.36467a-b)