Artemis is a white-furred, talking cat who serves as a guardian, advisor, and companion to Minako Aino, the civilian identity of Sailor Venus. He is a male character distinguished by a yellow crescent moon mark on his forehead and eyes that are typically blue in the anime adaptation. His origins lie in the ancient Silver Millennium, a lunar kingdom that was destroyed in a great catastrophe. Before the kingdom fell, Queen Serenity sent Artemis and his fellow guardian cat, Luna, to Earth's future to awaken and guide the reincarnated Sailor Guardians.

Artemis's core mission is to support the Sailor Guardians in their fight against evil. He is specifically responsible for Minako Aino, whom he awakened as a warrior long before the other Guardians were found. Initially, Minako operated under the alias Sailor V, with Artemis acting as her mentor and partner during her solo missions against the Dark Agency. He established a secret command center for her beneath the Crown arcade, using advanced computers and a Sailor V video game to communicate and gather intelligence. When the time came for the Sailor Guardians to unite, Artemis and Minako joined the team led by Sailor Moon.

In terms of personality, Artemis is portrayed as more easygoing and flexible than his counterpart Luna. He approaches his role with a sense of calm and often acts as a big brother figure to Minako, offering guidance and support while allowing her the space to learn from her own experiences. He is deeply loyal and cares for Minako not just as his charge but as a true friend, having been her sole confidant during her difficult early missions. He is also brave and willing to put himself in danger to help the team, though he rarely participates in direct combat. Despite his generally patient nature, he has a proud streak and can be critical of Minako's more frivolous or irresponsible moments, sometimes throwing small tantrums when she acts too childish for his liking.

A significant aspect of Artemis's character is his relationship with Luna. While the two work together as partners guiding the Sailor Guardians, Artemis often takes on a supportive and comforting role with her, particularly when she is worried or stressed about their charges. He harbors deep romantic feelings for her, though he can become flustered or jealous when other potential suitors appear. In the future, he and Luna are destined to marry and have a daughter named Diana, a kitten who becomes the advisor to Chibiusa. Artemis is shown to be a caring and affectionate father to Diana.

Artemis's role in the story is primarily informational and supportive. He is a source of knowledge about the Silver Millennium, often retaining more accurate and complete memories of the past than Luna. This is sometimes explained by the fact that the two cats agreed to suppress part of Luna's memories so she could focus on her task of training the true Princess. Artemis is responsible for delivering special transformation items and communication devices to the Sailor Guardians. In the Sailor Moon Sailor Stars season, he continues in this role as a trusted ally from the home base, assisting the team in their battles against new enemies and providing counsel from the sidelines. Unlike in the manga, the anime version of Artemis does not have the ability to take on a human form, nor is his origin from the planet Mau mentioned; he remains a talking cat throughout the series.