Ayu Daikuuji, the irritable and surly daughter of Sky Temple financial conglomerate's CEO, works incognito as a part-time waitress at one of the conglomerate's restaurants. This role fulfills a market research initiative demanding her identity remain secret. Alongside colleague Mayu Tamano, she handles waitressing duties.

Sporting pigtails and a distinctive snaggletooth, Ayu displays an abrasive, mischievous demeanor, frequently delivering comic relief through sharp interactions. Her trademark catchphrase, "You can go step in cat crap!", underscores her brash exterior. As a classic Tsundere (Type A) archetype and cited originator of the type, she balances her sharp tongue with occasional underlying compassion, demonstrated through practical assistance to others when needed.

Beyond comedy, Ayu and Mayu feature in episodic post-credit "Ayu-Mayu Theater" segments, depicting super-deformed comical scenarios unrelated to the main plot. Ayu appears in the main series, the OVA "Rumbling Hearts: Next Season," and video games including "Ayu-Mayu Alternative," "Daikuuji Temple in Crisis!," "The Eternity You Wish For," and its special fan disk. She also stars in spin-offs "Ayu-Mayu Gekijou" and "Daikuuji Kiki Ippatsu," which further explore her character.

Her given name, Ayu (あゆ), uses hiragana script without inherent meaning, distinguishing it from potential kanji interpretations like "friend," "love," or "excellence."