Mamoru Chiba is the civilian identity of Tuxedo Mask and the modern reincarnation of Prince Endymion, Earth's ancient protector. His surname "Chiba" blends the kanji for "earth" (地) and "place" (場), and his given name "Mamoru" (衛) means "to protect," signifying "Protector of Earth." Orphaned at age six in a car accident that killed his parents and induced retrograde amnesia, he grew up isolated, haunted by recurring dreams of an unknown girl urging him to find the Legendary Silver Crystal to restore his memories. These dreams drove him to adopt the Tuxedo Mask persona, operating covertly in a black tuxedo, cape, top hat, and white mask. Initially cold and sarcastic, Mamoru frequently clashed with Usagi Tsukino (Sailor Moon) over her academic struggles and hairstyle. Their relationship evolved from antagonism to romance after discovering their shared past-life identities as Prince Endymion and Princess Serenity, though his memories resurfaced slower than hers. As Tuxedo Mask, he supports the Sailor Guardians in battle by throwing roses, wielding a cane, and delivering motivational speeches, though his abilities vary. The manga and *Sailor Moon Eternal* depict him wielding the Golden Crystal (Earth's Sailor Crystal) with psychic powers like psychometry, dream-reading, and healing, while the anime emphasizes spontaneous transformations without named attacks. Mamoru endures recurring traumas: brainwashing by the Dark Kingdom in Season 1, forcing him to fight Usagi; memory loss in Season 2, splitting his psyche into the Moonlight Knight; and prophetic nightmares in the Black Moon arc, causing him to temporarily break up with Usagi to protect her. During the Dead Moon arc (adapted in *Eternal*), his connection to Elysion—Earth's sacred realm—causes a magical affliction when corrupted by Queen Nehelenia. A black rose manifests in his lung, inducing severe illness and coughing blood. This arc reveals deeper ties to Helios, Elysion's guardian priest, culminating in Mamoru awakening the Golden Crystal to aid Eternal Sailor Moon in purifying Nehelenia's darkness. His relationship with Usagi solidifies across the series, marked by an airport engagement in the manga and a future as King Endymion of Crystal Tokyo with their daughter, Chibiusa. He demonstrates protective instincts toward both, notably sustaining Chibiusa's life force with his energy during the Infinity arc. Non-anime media depict variations: the live-action series portrays him as a thief seeking the Silver Crystal, while musicals explore alternate dynamics like Beryl as his past-life fiancée or Pluto's unrequited love. Mamoru's development centers on overcoming isolation and trauma to embrace his role as Earth's guardian. His academic pursuits include medical studies, reflecting a desire to heal others, and his personal growth transitions from cynicism to selfless devotion.