Saki Kawasaki is initially portrayed as a calm, serious, and somewhat aloof individual. When first introduced, she appears to be a loner, often seen by herself and avoiding interaction with others. In her debut scene (Episode 5, Volume 2), she is spotted holding a lighter, which led to early speculation about her being a smoker though she is only shown playing with it, and the anime or light novel never explicitly confirms any smoking habits.

Saki tends to come off as cold and distant. She is blunt, stubborn, and socially withdrawn, often avoiding small talk and keeping her personal matters private. Her rough image is further emphasized by her frequent tardiness, disheveled appearance, and terse manner of speaking, which gives others the impression that she is a delinquent. However, her perceived aggressiveness is largely a result of social awkwardness and difficulty expressing herself rather than any ill intent.

As the series progresses, Saki’s more compassionate and responsible side becomes apparent particularly in relation to her family. She is shown to be a devoted older sister, regularly texting during class (presumably with her younger brother Taishi), often with a rare smile. She also runs errands involving her younger siblings, such as Keika and Taishi, and works part-time jobs to support her family and fund extra lessons to improve her academic performance.

Despite leaving her night shifts and cutting down on part-time work, Saki continues to appear tired and disinterested in typical high school social life. Her withdrawn attitude reflects a general lack of enthusiasm for the usual teenage concerns rather than laziness or indifference.

Her peers have varying impressions of her: Saika Totsuka remarks that she is rarely seen being friendly with others, and Yoshiteru Zaimokuza describes her as solemn and aloof. In contrast, her younger brother Taishi sees her as kind-hearted and serious.

Saki Kawasaki is a teenage girl with a slender build and slightly above-average height. She has long, pale blue hair that extends to her waist, accompanied by short, uneven bangs. Notably, she has a beauty mark beneath her right eye. Her eye color varies slightly between anime seasons appearing emerald green in Season 1 and pigeon blue in Season 2. Hachiman Hikigaya once remarked that her legs looked like they were “made for kicking,” emphasizing her athletic appearance.

Saki typically wears the standard Sōbu High School uniform, though in a distinctly unorthodox manner. Her shirt is often left untucked with two buttons undone, and she frequently forgoes the school blazer. When she does wear it, the blazer is left open and unbuttoned. She is sometimes seen with a gray cardigan tied around her waist. Her uniform has been described by Hina Ebina as heavily modified, reflecting her rebellious and independent image. Saki also wears handmade scrunchies in her hair and around her wrists, adding a subtle personal touch to her overall appearance.

Saki Kawasaki is skilled in various domestic tasks, largely developed through caring for her younger siblings from a young age. She is proficient in cooking, having regularly prepared meals for her family during her middle school years. She also demonstrates strong sewing abilities, both by hand and with a sewing machine. These skills are showcased during school events, such as when she helped design costumes for the class play at the Cultural Festival and created outfits for the Athletic Festival. Her talent in tailoring is further highlighted by Hina Ebina, who notes the handmade scrunchies Saki wears and the custom modifications to her school uniform.

In Volume 2 of the light novel, her listed skills include karate and making soft toys, suggesting a mix of both physical and creative talents.

Saki is also shown to be moderately athletic. She participates in events during the school’s athletic festival and contributes to school activities such as being part of the broadcasting team, working alongside Hina Ebina and Yumiko Miura.

The name Saki (沙希) is composed of the kanji 沙 meaning “sand” and 希 meaning “hope.” Her given name is also embedded within her family name, Kawasaki (川崎), which is made up of 川 (kawa), meaning “river” or “stream,” and 崎 (saki), meaning “cape” or “peninsula.” This pattern, where a character’s first name appears within their surname, is shared with several other characters in the series, including Yui Yuigahama, Yukino Yukinoshita, Rumi Tsurumi, and Meguri Shiromeguri. This subtle naming choice adds a layer of thematic consistency to the series’ character design.