Aiko Kudō is a Top 10-ranked student in Class 2-A at Fumizuki Academy, having transferred at the end of her first year. She possesses light green spiky hair, hazel eyes, stands 5'2" (157 cm) tall, and weighs 46 kg (101 lbs). She is taller than Mizuki Himeji and similar in height to Minami Shimada.

Friendly, easy-going, and mischievous, Aiko refers to herself using the masculine pronoun "boku." She frequently teases Akihisa Yoshii and Kouta Tsuchiya with perverted remarks, provoking comedic reactions like nosebleeds, yet remains the only main female character who doesn't intentionally harm males. Her interactions suggest romantic interest in Kouta, shown by efforts to draw his attention, such as encouraging him to look at her swimsuit and quickly volunteering as his partner during a Test of Courage.

Aiko excels with electronic gadgets, often using a micro-recorder to capture and manipulate conversations. She splices recordings to create misunderstandings, particularly causing trouble for Akihisa. Academically, she shines in Health and Physical Education (PD/H/PE), studying it "practically" rather than theoretically like Kouta, leading to a friendly rivalry between them.

Her Shoukanjuu wears a sailor-style school uniform and wields a battle axe enhanced with electrical accessories. An alternate occult version manifests as a Noppera-bou (faceless spirit), which Yuuji Sakamoto interprets as symbolizing her reluctance to reveal her true self.

Background details include a simulated future scenario where she worked as a doctor, though not a definitive outcome. Another simulation involving Kouta Tsuchiya depicted a hypothetical son inheriting Aiko's appearance and hairstyle but possessing Kouta's eyes. This son exhibited a serious demeanor, reciting Confucian texts, yet retained a tendency toward eroticism reflecting Aiko's mischievous traits.

Her name, Aiko (愛子), means "love child," and Kudō (工藤) combines "worker" and "wisteria."