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- Main article: Haruka Nanase
Aki regards Haru highly, and she and her lost scarf in the river beneath Misagozaki Bridge are a major catalyst for his development. She puts in effort to understand his viewpoint, mentioning that she would have continued staring on glumly as her scarf floated away if he hadn't told her to leave it be. Because of Haru being attentive to her, Rin thinks out of everyone, it's more likely that she, along with Makoto, can get through to Haru about joining him in the medley.
She, like Rin, believes that Haru would do well swimming in the medley, wanting to see a Haru who can rely on others.
- Main article: Shota Yazaki
Aki seems to hold an admiration for her older brother, as his being part of the swim club was the initial reason she also joined.
However she can also showcase annoyance and disappointment in her brother that she isn't afraid to express, such as when her brother got upset after he lost to Haru in a race and got banned from club activities. She calls him stupid and impatient for it, stating that he always orders people around and acts all self-important right away.
- Main article: Makoto Tachibana
Aki and Makoto have a good relationship, with the latter affectionately calling her 'Zaki-chan,' much like he would later call Rin's sister and Iwatobi's manager 'Gou-chan.' Aki turns to him to understand Haruka more than she does, and Makoto is supportive of her as a friend, such as when she loses her scarf, and when she forwards the idea of planting flowers around a lonesome cheery blossom tree.
Late in High Speed! they share excitement over each other's medley team doing well, culminating in a high five between the two of them.
- Main article: Nagisa Hazuki
From the beginning, Nagisa has called Aki "Zaki-chan" affectionately, much like he later calls Gou "Gou-chan." Aki regards Nagisa as little brother-like, but becomes very taken aback by his forward eyes, thinking of how their reflection lays bear the swimmer she truly wants to be.
She's shown to yearn "to swim with [her] honest feelings, like Nagisa does", and hates herself for unable to answer him with a certainty to her words.
- Main article: Rin Matsuoka
Unlike Makoto and Nagisa, Rin calls Aki the more formal "Yazaki-san." At one point she's led to believe due to their joking around that Rin is being bullied by the boys, and promptly scolds them on his behalf. She connects with him through how much they both want Haru to join the medley, confirming during their conversation that she thinks of Rin as someone with a large personality, even joking with him over it.
In her own POV, she's shown to wonder over how he's always "running towards somewhere," seeking something.