Kazuma met Aqua first before anyone else in the newly reincarnated fantasy world. Even though Kazuma finds Aqua annoying and often useless, the two are inseparable, and are almost always seen together. They rely on and care for each other more than they would like to admit. For example, Aqua shows visible concern when Wiz uses Drain Touch on Kazuma for the first time. Aqua feels that Kazuma should show her more respect, considering how often she resurrects him. Regardless, she also addresses him with honorifics like "-san" or "-sama". Despite the fact that they have been together the longest, their relationship thus far remains the only one that is completely platonic on both sides.
They get along well as fellow party members and are also quite alike in some ways, allowing them to sympathize with each other even when not adventuring. When Kazuma stops accompanying Megumin to cast Explosion at Verdia's castle, Aqua secretly goes with her instead, suggesting a good bond between the two.
They get along since Darkness is another party member. Despite this, they have seldom interacted with each other. Darkness seems to trust Aqua's intuition, sharing her unease when they come across Mitsurugi. Aqua isn't bothered by Darkness' masochism.
Aqua likes to make life difficult for Wiz, often going to her store to purify items and slander them outside their shop. She also rubs holy water on the shop's door handles, scalding Wiz's hands in the process. Despite this bullying, Aqua is genuinely fond of Wiz. She often visits the lich's shop whenever bored and states that she doesn't want to kill Vanir because it would make Wiz sad.
Aqua is Eris' senpai as a goddess. She knows of Eris' breasts pads, as well as her secret trips to the fantasy world. Aqua doesn't particularly like Eris, and is envious of the latter for being the more worshpped of the two, even though Eris is considered to be a lower-class goddess.