Azabu-Juuban, Minato-ku, Tokyo
Guardian of Sailor Moon(anime)
Humanoid psychic projection
In the Anime
After Mamoru Chiba died at D Point from injuries sustained in his fight with Queen Beryl, Sailor Moon succeeded in using the Silver Crystal to defeat the Dark Kingdom forever. While her use of the Crystal destroyed the surrounding area, its power allowed her to bend reality to her will, resulting in herself, the rest of the Sailor Team, and Mamoru being transported back home to Azabu-Juuban alive and well, with no memory of each other or their battle with the Dark Kingdom. When the Makaiju arrived on Earth and Cardians began appearing, Luna and Artemis were forced to trigger the dormant memories of the Sailor Team, allowing them to transform once again. The team was soon reunited, but with one notable absence: Tuxedo Mask. Since Mamoru was not a Sailor Senshi, Luna was apparently unable to restore his memory. Thus he continued life as normal, with no memory of Tuxedo Mask, Sailor Moon, or the fondness he had developed for Usagi.
However, shortly after the Sailor Team was reunited, a mysterious figure began appearing to assist them in much the same way that Tuxedo Mask had. This man, who called himself the Moonlight Knight, was dressed in a white Arabian costume, and used white roses and a scimitar as weapons. When he first appeared during the battle with the Cardian Falion, Sailor Moon was immediatedly struck by the resemblance he shared with Prince Endymion. However, her belief that the Moonlight Knight was Mamoru was shattered when, on their next encounter, the Moonlight Knight appeared in the same room as Mamoru. The Sailor Team continued to investigate the Moonlight Knight's identity, for a while suspecting that he was Seijuurou Ginga. Makoto later decided that this could not be the case, having noted their vastly differing attitudes towards love.
The truth behind the Moonlight Knight's identity was stranger than anyone had imagined. When Mamoru's memories had been locked away, his desire to protect Sailor Moon remained strong. After Sailor Moon was reawakened, this subconscious desire manifested itself in the form of the Moonlight Knight. Although apparently nothing more than a psychic projection, the Knight had a physical presence and could interact with his environment. He revealed his identity to Sailor Moon during their confrontation with the Makaiju, at which point Mamoru's memories were beginning to return. He then merged back into Mamoru's body for the final time, restoring his memories and ability to transform into Tuxedo Mask.