Artemis

Artemis is the white cat, he's SailorVenus' guardian and guide. He is not nearly as bossy or mean as Luna, he's kind, courageous, emotional and a klutz, =) and he's also very funny. He's no less dedicated than Luna to their mission to guide the Sailor Senshi -- he's just as smart and wise as Luna is.
His relationship with Minako -- whom he calls "Mina" -- is fairly interesting. It is very obvious that they are very fond of each other, and they understand each other quite well, but one could say Artemis takes more abuse from Minako than Luna takes from Usagi, but Luna can defend herself quite well. =) Beyond this, Minako and Artemis seem to be each other's best friends, always watching out for each other, even if Artemis does get very little respect from Mina-P. =)

In a way, and because SailorVenus' unique status as the first senshi ever, and Artemis as her constant guard and companion, no one understands Minako quite the way Artemis does.
Artemis is quite courageous for a furball, too. =) He will attack any enemy when it becomes necessary, but having no cool Senshi powers, he ends up in pain fairly often. He has crush on Luna from the very beginning, but Luna is often falling in love with humans and realizes her true love has been Artemis much later. In the future, they have a kitten, Diana. Artemis has once been accused of falling in love with a human, an unfounded accusation, unlike Luna's. =)
Artemis is quite close to the Inner senshi, but he gets even less respect than Luna does. =) Luna also tends to get a lot more sympathy, but Artemis is still quite loved and esteemed, just taken for granted. =)
Artemis' protective feelings for the ones he loves, especially Minako-chan and Luna, are very strong, and he seems to take his role as a parent quite seriously, unlike some future queens we know. =) In the SuperS season, Artemis has to play daddy to kawaii daughter Diana, and doesn't hide his sorrow when she leaves for the future. =( We don't get to see him much in the SailorStars season, tho.