Artemis is the white feline guardian who serves as the devoted companion and advisor to Minako Aino, the heroine known as Sailor Venus. Originating from the ancient Silver Millennium, the former kingdom of the Moon, Artemis was sent to Earth alongside his counterpart, Luna, to awaken and guide the reincarnated Sailor Guardians in their mission to protect the planet and the princess of their lost home. His memory of the Silver Millennium remains remarkably clear, which allows him to provide crucial context and details about their true purpose that Luna does not always possess.

Throughout the events of Sailor Moon R, Artemis acts as a steady and supportive presence. His personality stands in contrast to Luna's more stern and controlling demeanor. While Luna often lectures and pushes Usagi Tsukino, Sailor Moon, toward her duties with a maternal strictness, Artemis is considerably more easygoing and relaxed. He relates to Minako not as a disciplinarian but more like a patient and understanding big brother, offering advice and guidance without sharpness or judgment. Although he is occasionally exasperated by Minako's dramatic romantic interests or her impulsive behavior, he never resorts to making snide or cruel remarks at her expense, instead maintaining a fundamentally kind and compassionate attitude.

This gentler temperament does not diminish his dedication to the mission. Artemis is deeply loyal and takes his role as a mentor and strategist seriously, working to ensure the safety of the Sailor Guardians and the success of their objective. He is shown to be resourceful, capable of using computers to gather intelligence and communicate with allies, and he demonstrates a willingness to place himself in danger to protect others, even rushing into battle despite his small size and physical vulnerability to aid a fallen comrade.

His most significant relationship is, of course, with Minako. He trained her extensively during her time as the solo hero Sailor V, and this bond deepens as she integrates into the larger Sailor Moon team. He cares for her not only as a charge but as a close friend, and he is often the sole confidant for her personal struggles. Artemis also shares a close and caring dynamic with Luna. He frequently comforts her when she becomes stressed or worried about the Guardians, and he makes no secret of his deep admiration for her. Their implied romantic connection is a defining aspect of his character, and it is later confirmed through the existence of their future daughter, Diana, a small kitten who appears from the 30th century. This future role as a father is portrayed with warmth, as he is shown to be a good and affectionate parent to Diana.

In terms of abilities, Artemis possesses several unusual traits. He has human-level intelligence and the ability to speak, with the crescent moon mark on his forehead serving as the source of this power. He has a demonstrated proficiency with technology, as seen when he uses a video game at the Crown Game Center arcade to test and guide Usagi before revealing his identity. While Luna often produces special items and transformation tools, Artemis is more frequently shown delivering or providing these crucial devices to the Guardians. He also possesses a deep knowledge of the past and the mission, making him a valuable source of information. While not a frontline fighter, his bravery and quick thinking are crucial in several situations, such as when he distracts a monster to protect a civilian, allowing Sailor Moon to transform and defeat it.