According to "Goshidaisho" (a commentary book written by Kanera ICHIJO on "Koke Shidai," which is a classic rule book about ceremonial and public functions), bowing twice in the beginning indicates respect for the Imperial edict, and the following dance expresses joy for receiving a favor.
『江次第抄』によれば、初め再拝するのは詔命を欽ぶ意で、後に舞踏するのは恩恵にあずかるのをよろこぶ意であるという。