Kunzite, known as Malachite in the English anime, is the fourth and final member of the Shitennou. He wields a shortsword and is described by Takeuchi as the greatest among the four, embodying the majesty of an Arabian king. She admits to having a special fondness for him as a character. At around 25-26 years old, he leads the Dark Kingdom's Middle Eastern Division and is named after the mineral kunzite (or malachite in the dub).
In the manga, Kunzite initially serves in an advisory role to Zoisite, helping the younger king devise strategies for energy collection. He shows little concern for his fellow Shitennou and remains impassive when Jadeite, Nephrite, and Zoisite are killed. Queen Beryl informs Kunzite that if they recover the Ginzuishou, the fallen Shitennou could be revived. Following her orders, Kunzite attacks the Sailor Senshi at the Tokyo Tower and defeats them swiftly. When Tuxedo Mask sacrifices himself to save Sailor Moon, she regains her memories as the Moon Princess, and the Ginzuishou appears, its light affecting everyone, including Kunzite. This causes him to recall his past and struggle between loyalty to Beryl and Endymion. Witnessing the brief rebirth and subsequent decomposition of his fellow Shitennou, Kunzite captures Mamoru and brings him back to the Dark Kingdom. After questioning Beryl about reviving the Shitennou, she intensifies his brainwashing by implanting a shard of kunzite crystal into his forehead, turning him into a mindless zombie. In a rage, Kunzite attacks the Senshi again but is ultimately defeated by a Sailor Planet Attack, leaving only the piece of kunzite stone behind. In the final battle against Queen Metaria, Kunzite traverses dimensions to inform Mamoru of Metaria's weakness, enabling him and Usagi to defeat the demon queen.
In the anime, Kunzite is first seen plotting with Zoisite against the second king, Nephrite. They are portrayed as lovers, with Zoisite seeking support from Kunzite. Together, they collect all seven Rainbow Crystals, but Zoisite's attack on Tuxedo Mask costs him his life and reveals Sailor Moon as the Moon Princess, awakening the power of the Ginzuishou. Zoisite's death plunges Kunzite into depression, though his loyalty to Queen Beryl remains unwavering. He follows Beryl's instructions to bring the injured Mamoru back to the Dark Kingdom, where he is transformed into an agent of the Dark Kingdom. Despite resenting working with Endymion, Kunzite carries out his assignments loyally. Growing suspicious of Endymion's interference, Beryl tasks Kunzite with monitoring him. After many defeats, Endymion is temporarily cured of Beryl's brainwashing and taken back to the Dark Kingdom. The Senshi resolve to find the entrance to the Dark Kingdom, recover Mamoru, and end the threat once and for all. Kunzite battles them at D Point, restoring their past memories of the Moon Kingdom. In a final desperate attack, Kunzite uses an energy boomerang, taking out all the senshi except Sailor Moon. His projectile is deflected back at him, leading to his demise as he cries out for Zoisite, hoping to meet him on the other side.
