Saki Daimonji is the eldest of the three Daimonji sisters, alongside Emi and Yu. She is an adult female with black hair styled in a bun and purple eyes, though one source lists her eye color as red. Her typical attire is a kimono, reflecting her occupation as a geisha, and she accessorizes with a hair ornament. She stands 1.64 meters tall with measurements of 86-58-84.

Saki leads her sisters as a three-member alliance team serving as the third opponent faced by protagonist Aya Iseshima in the Platonic Heart tournament. In combat, Saki wields knives, throws hairpins, and employs a wagasa (Japanese paper parasol). This parasol functions defensively as a shield and offensively through whirling motions. During their combined special attack, Saki typically positions herself at the front to lead the assault.

Following their collective defeat by Aya, Saki and her sisters share the standard consequence for tournament losers orchestrated by Miko Kazuki and her co-conspirators: enslavement and mental conditioning. This conditioning reduces them to a state of psychological breakdown and obedience.