When Darkness was young, she didn't have any friends, so she prayed to Goddess Eris daily for one. As if to answer her prayers, Darkness met Eris, who had disguised herself as Chris after one of her church visits. They became best friends ever since, with Chris being Darkness's partner before she joined Kazuma's team. Recently, Chris gotten busy recently due to her newfound responsibilities as a Goddess filling out for Aqua's old duties, causing her to be away from Axel most of the time. Nevertheless, Chris and Darkness are still very close and still meet up whenever possible.
Kazuma refused Darkness' initial approach to join the party but eventually conceded. While she fulfills his fetish of an "onee-san with great figure", her personality turns him off. Despite this, he often looks at her with lecherous eyes. Vanir teases that both Darkness and Kazuma have affection for each other but fear crossing the line of adventurer comrades, which greatly embarrassed the both of them upon hearing this. Often, Darkness blurts out perverted thoughts, to which Kazuma often snarks at either verbally or mentally. However, she also seems to enjoy his verbal abuse, much to Kazuma's dismay. Though he considers her the most useless member in his party, he does sincerely care for her and vice versa. Darkness also sees Kazuma as a good friend who she can rely and trust on. Later on in the story, Darkness starts to develop feelings for him after he saved her from her arranged marriage.
They get along well enough to converse normally. She isn't easily annoyed by Aqua's stupid antics. Aqua also helped dispel the curse given to her by Dullahan.
They get along well enough to converse normally. She even took the curse from Dullahan that was initially intended for Megumin.