Nephrite is the second highest in command of the shitennou; he is second only to Kunzite. He is the commanding officer of the North American division on Earth. According to the Materials Collection, his estimated age is nineteen, and he is "emotional and intense." Takeuchi also describes him as an oldest-son type and states that his pride will likely get him killed right away.
Nephrite's appearance is short-lived in the manga, but the glimpse we do see of him portrays an arrogant spirit and high ambition. He does not heed the advice of others and prefers to work alone. After Jadeite's two failed attempts, Nephrite begs to be allowed his chance to serve the Dark Kingdom. He promises quite arrogantly to not only gather energy but to also locate the ginzushou. Although his plans succeed in obtaining great amounts of energy, his ultimate goals are foiled by Sailorjupiter.
Nephrite's power is his shadow. This field of black energy can take on the form of any person and possess objects and people. He uses it to confront the senshi without putting himself in danger. The shadow possesses Princess D, the notorious Ghost Bride mannequin, and Motoki.
With these negative characteristics also comes strong loyalty. Nephrite criticizes Jadeite's schemes, but he vows revenge when Jadeite is struck down by Sailormars. His determination to find the ginzushou is fueled by the thought that with it Jadeite will be revived. Although it seems as though Nephrite does not get along with the other kings, his devotion to them is unquestionable.
The anime plays up Nephrite's arrogance quite a bit. He lives among the people of Tokyo using the alias Masato Sanjouin. He drives an expensive car and dwells in a magnificent house. He also has the ability to read constellations and relies on stars for guidance. His loyalty to the shitennou is not nearly as evident, either. (The bond among all four has been all but destroyed, except for the exaggerated relationship between Kunzite and Zoisite).