Akari Yomatsuri is a seventeen-year-old girl who serves as a key member of the midsummer knights, the primary team of protagonists. She is a slender teenager with lightly tanned skin, short orange hair, and purple eyes. Her hair is typically styled with two purple clips and a smaller green one. Her casual outfit often consists of a slightly short yellow tank top that exposes her midriff, paired with green shorts and white and yellow wedge shoes.

Akari is the daughter of the commander of the Tanegashima Space Center, though her parents are divorced, and she has had little contact with her father for several years due to his work. This family situation led her to spend a great deal of time on the internet during her formative years, where she cultivated her defining skill as a genius-level hacker.

Her personality is lively, cheerful, and energetic, though it is marked by several distinctive quirks. The most notable of these is her insistence on referring to herself as a magical girl, describing her various technical skills as spells. She often dramatizes her own role in the group, humorously lamenting that she is losing heroine points or that her chance to be the main protagonist is being stolen by others, a frustration she frequently directs towards the more naturally charming Hana Mutou. She has a habit of saying the phrase logical, logical, usually when performing her computer-based magic. Despite her comedic and attention-seeking exterior, Akari is also a serious, calculating, and reliable individual who becomes a crucial support for her friends during battle. She demonstrates a notable lack of self-consciousness on occasion, such as when she performs what she calls her Belly Button Forte, a silly trick meant to cheer up a friend, which she later teaches to Hana.

In terms of abilities, Akari is a seventeen-year-old genius hacker of wizard-class skill. Her hacking prowess is so advanced that she can intercept military satellites, break into Globes confidential communication lines, and even find backdoors into the enemy's own machines. This skill set makes her a primary target for the antagonistic planetary gears, who become sufficiently alarmed by her abilities to attempt her capture. Beyond hacking, she is also an adept pilot and can remotely control the Earth Engine Impacter, a giant robot, from a ground-based computer, though she notes that direct control is easier. Her interests extend beyond technology, as she also engages in foreign exchange trading as a hobby, calling it social study, and seems to have a propensity for gambling.

Within the story, Akari is introduced as an initial observer of the strange phenomena heralding the aliens arrival. She takes control of the Earth Engine Impacter during a battle to assist the protagonist, Daichi Manatsu, and formally introduces herself to the group as magical girl Akari-chan. She acts as a flight director and information analyst, providing essential support from the rear lines. Her key relationships include a friendly but often frustrated dynamic with Hana Mutou, whose natural charm she envies, though she shares a close bond with her. She also develops a romantic relationship with Teppei Arashi, another member of the team. Her relationship with her estranged father, Nishikubo, is initially distant, but his efforts to reconnect include having the team lodge at his home.

Over the course of the series, Akari is a character who enters the story with a strong sense of her own identity, and thus does not undergo a dramatic personality shift. However, her role as the comedic magical girl becomes somewhat less pronounced in the latter part of the narrative as the story focuses more on the serious stakes of the conflict. Her reliability, quick thinking, and loyalty to her friends remain her most consistent and valuable traits throughout the series.