Nephrite keeps the same appearance in the anime as he does in the manga. His uniform is similar in style as his predecessor; a blue-grey suit with a yellow trim with epaulettes on his shoulders; a black belt, tall black boots, white gloves, and small yellow stud earrings.
Unlike his predecessor, Nephrite did not believe that attacking large numbers of people indiscriminately was an effective way of gathering energy, but rather targeting one person who held a large amount of energy. A firm believer that human destiny is guided by the movements of the stars, Nephrite used astrology to perform inside his operations base (a large mansion located in a wooded area of the vicinity of Tokyo) to help him concentrate him locate individuals where their "energy potential" would be at its maximum. Once he discovered his target, he would meet with them, under the guise of an entrepreneur and socialite named Masato Sanjouin, use an item of their's that usually symbolizes their talent and mark it with a special symbol. Doing so placed a Youma in the object, and the person's interest would turn into obsession where the victim would become determined to better their craft and once the individual reached the peak of their energy potential, the youma would emerge from the object and steal the victim's energy. But once the youma was defeated by Sailor Moon, the energy would be restored to the victim.
As Masato Sanjouin, it wasn't long before he found his first victim: a young girl named Rui Saionji, a gifted tennis player and close friend of Naru Osaka's. Posing as a professional tennis coach, Nephrite, offered her some basic advice before implanting a Youma inside her tennis racket via his evil crest. Upon peaking in her energy potential, he released the Youma Tesuni who despite stealing her energy was defeated by Sailor Moon with a lot of help from Tuxedo Mask.
Nephrite managed to locate his next victim, Mr. Kunitachi, who was a gardener for a park. Mr. Kunitachi was perhaps the only victim he indiscriminately attacked where he was able to exploit his emotions over the destruction over his beloved park by intensifying his strong feelings. Not only did Nephrite steal his energy but also the energy of the park’s animals through his evil crest which was implanted on his hat and the subsequent release of the Youma Petasos. However, in typical fashion, Sailor Moon, Sailor Mercury, Sailor Mars with assistance from Tuxedo Mask disposes of Petasos. Similarly the Youma Widow who was implanted via Nephrite’s evil crest in a piece of material belonging to Usagi's sewing class teacher, Ms. Higure Akiyama and Cameran who was implanted via Nephrite’s evil crest inside the camera of the award winning photographer Kijin Shibakawa were also disposed of by Sailor Moon's Moon Tiara.
With the destruction of his three Youmas, more is learned about his character as a curious Queen Beryl asks of his progress in dealing with Sailor Moon, Sailor Mercury and Sailor Mars in episode 18. His determination in pursuing tasks individually reveal his great sense of pride; a tool which is used to defy and irritate Queen Beryl as well as an asset that a jealous Zoisite exploits while he subtly tries to ruin his reputation and ultimately eliminate Nephrite. The subsequent failure of his next Youma Jumeau greatly helped Zoisite for it allowed him to continue to patronize Nephrite of his shortcomings as Queen Beryl, who by this time lost confidence in Nephrite, reprimanding him for his inadequate collection of human energy and even threatening him with the same ultimatum as his predecessor Jadeite: the death of Sailor Moon or share in his punishment of "Eternal Sleep".
Through the intonation of the stars in his hideout, Nephrite learns that Tuxedo Mask is Sailor Moon's greatest weakness. With some persuasion, Queen Beryl allows Nephrite to disguise himself and impersonate Tuxedo Mask so he can exploit Sailor Moon's “foolish love" by trapping and learning of her identity before killing her. As part of his plan, Nephrite’s mails bogus love letters to junior high school students within certain areas of Tokyo (including Usagi and Rei). Unfortunately, his plan fails when Naru correctly deduces that he was behind the distribution of bogus love letters to the female students. Suspecting that she was Sailor Moon, Nephrite “led her on” to test if she would walk into his trap at the Shinjuku MS Department Store. His suspicions were seemingly confirmed when she was naive enough to attend the Shinjuku MS Department Store earlier than expected and recognize Nephrite’s alter ego inside the Tuxedo Mask disguise. After confronting her in his Tuxedo Mask outfit demanding that she “reveals herself”, he drained all of her love energy despite the latter pleading that she was not Sailor Moon. When the masquerade was exposed after he was discovered draining Naru of her energy by Usagi, she quickly changed into Sailor Moon to confront Nephrite. Once Nephrite fully revealed his true identity to Sailor Moon, he scares her with an illusion of his clones before creating an illusion of the star Regulus to whom he calls upon its power. The illusion of the star transforms into the constellation of Leo which becomes a white lion. Had it not been for Tuxedo Mask striking Leo on his face, Sailor Moon would have been fatally wounded. Returning his favor, Sailor Moon helps Tuxedo Mask battle Regulus with her Moon Tiara Action attack, only for it to fail her as it merely stuns it. Upon recovering, it continued his pursuit of Sailor Moon and Tuxedo Mask. He is recalled by Nephrite after he successfully traps the retreating Sailor Moon and Tuxedo Mask inside an elevator rigged by Nephrite. However, both Sailor Moon and Tuxedo Mask escape from Nephrite's trap and certain death with the help of Sailor Mercury and Sailor Mars.
Although Nephrite failed to kill Sailor Moon, Queen Beryl becomes very impressed with the amount of love energy drained from Naru Osaka and as such, waivers Nephrite’s punishment. But this was not the only means by which he had unwittingly profited from this scheme, for it also brought to his attention the fact that Naru was fawning over his alter ego Masato Sanjoin. Through the intonation with the stars in his hideout, Nephrite decided to continue pursuing her and exploit this valuable commodity for his own personal gain.
Having avoided Queen Beryl’s punishment of Eternal Sleep, Nephrite was allowed to continue in his energy gathering efforts in reawakening Queen Metaria. After performing inside his operation’s base intonation with the stars regarding his next target, Nephrite decided that the time was right for him to use his two powerful youma Castor and Pollux. Though seemingly unbeatable by the power of their friendship (as symbolized by their bound tails) and their ability to mimic both Sailor Mars's and Sailor Mercury's attack, the bound from which they drew their strength from weakened as they argued over how who should defeat their opponents. The distraction created from their bickering gave Sailor Moon, Sailor Mercury and Sailor Mars the opportunity to eliminate them once and for all. “It was after this defeat that Nephrite finally realized how much he had underestimated the strength of Sailor Moon, Sailor Mercury and Sailor Mars as well as in just how desperate a situation he was in, and that the only possible way he had left of redeeming himself was to find the Silver Crystal. It was an obsession that would ultimately prove to be his undoing.
When Queen Beryl learned that the Diamond Kingdom possessed a secret treasure, she designated Zoisite to investigate as to whether or not it was the Silver Crystal. However, his assignment was snatched from him as Queen Beryl believed that Nephrite's desperation after his recent string of failures would be the best motivation into working harder and succeeding. Regrettably, this was not the cast as this venture proved to be both a waste of time and resources for Nephrite. After going through all the trouble of implanting his last youma, Soul Shadow, inside Naru's body and using her as a middleman to pass Soul Shadow onto Princess D so the latter could steal the treasure. Not only was the Soul Shadow destroyed by Sailor Moon's tiara, but the legendary secret treasure was nothing more than a priceless 2000 carat diamond statue of the Diamond Kingdom's first princess.
Nephrite and Zoisite had a tumultuous relationship, and Zoisite took pleasure in Nephrite's failed schemes, in the hopes that he would be punished with Eternal Sleep and he would not have to compete with Nephrite in searching for the Silver Crystal. After constant failures, Nephrite refused to answer Queen Beryl's summons and Zoisite taunted him, before learning about his continued efforts to find the Silver Crystal, and Zoisite sent his youma, Yasha to spy on Nephrite. When Nephrite called upon the stars to locate the Silver Crystal, he was delivered the Black Crystal, which showed him an image of Naru. He approached her as Sanjouin, asking for her to find the Silver Crystal, but she believed one of the jewels in her mother's store to be it. After she delivered it to Nephrite, he tested it to find it to be a simple jewel but the Black Crystal still only reacted to Naru. Before he could take Naru, the Sailor Senshi arrived and fought the commander, but Naru stood in the way before Sailor Moon could finish him with her tiara. Yasha attacked the group, trying to get the crystal from Nephrite and almost hurt Naru but was destroyed by Sailor Moon and Nephrite left.
Later, he asked Naru who Sailor Moon's true identity was, saying he wanted to fight alongside the Sailor Senshi against Queen Beryl. Hearing this, Zoisite had three youma called the Plant Sisters kidnap Naru Osaka's, but not before she called Usagi, whom Nephrite assumed (correctly) was Sailor Moon. He set a trap for her and watched her transform, now able to attack her whenever he wanted. Tuxedo Mask arrived at the scene, but at that moment Nephrite sensed that Naru was in danger, and went to the warehouse to save her from the three monsters, nearly killing one of them with his sword. He received a cut in the process. He and Naru assumed they escaped the youma, but the monsters returned and one of them, stabbed Nephrite with long huge poisonous thorns. As Naru tried removing the thorns, they were attacked again by the youma and Nephrite defended Naru, and dropped the Black Crystal, which was confiscated by Zoisite. The three Sailor Senshi arrived and destroyed the youma, and Nephrite died and dissolves into dust, leaving only the bandage Naru Osaka's put around the cut on his arm as she cried in despair.
- Starlight Attack
- Nephrite also had the ability to create illusions, causing Usagi to see her path distorted before transforming into Sailor Moon.
- He could also call down lightning from the sky.
- He displayed skills in swordplay and martial skills, able to battle three youma at once.
Nephrite is named after a variety of jade of the same name.
The kanji in his surname for his alias as "Masato Sanjouin" means "three" (三), "article" (条) and "temple" or "institution" (院). His first name means "right man", "true man", or "holy man" (正人).
- Nephrite was seen driving a Ferrari Testarossa 512 TR in some of the episodes in which he appeared.
- In the manga, Nephrite is killed by Sailor Jupiter. In the anime, they never meet since Nephrite is killed by Zoisite's youma the episode before Sailor Jupiter's introduction.
- In the first anime, Nephrite is the first villain to show redeeming qualities in the series.
- It is revealed in his final episode, Nephrite's blood is green.
- His rivalry with Zoicite is vey similar to the one between Rubeus and Esmeraude later in Sailor Moon R except that rivalry is only present for two episodes.