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 and care for each other more than they like to admit, even working hard together when first arriving at the Fantasy World, as well as Aqua showing visible concern for Kazuma when Wiz uses drain touch on him for the first time. Aqua feels Kazuma should show her more respect, considering how often she resurrects him. Despite the time the two spent together being the longest in the Kazuma's party, their relationship thus far remains the only one that is completely platonic from 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. When Kazuma stopped accompanying Megumin to cast Explosion at Dullahan's Castle, Aqua secretly went 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.
She likes to make life difficult for them, often going to their 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 does has a fondness for Wiz. She often visits the lich's shop whenever bored and stated that she didn'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 her for being more worshiped than herself even though Eris is considered to be a lower-class Goddess.