This man is the living embodiment of "tall, dark, and handsome." He's also very intelligent, courteous, sensitive, perceptive, and immensely romantic. It's a pity that he's not available -- his heart and soul belong to the Moon Princess, now and forever.
Chiba Mamoru was in a bad car accident on his sixth birthday, and it destroyed his memory and killed his parents, leaving him with nothing. Even his name was not his own; it was given to him by the hospital where he recovered. He grew to be a serious, intellectual, and very handsome man, studying to be a medical student; at the beginning of the series, he attended Moto Azabu, a very elite school. By night, he roamed the city in a tuxedo, a mask, and a black cape, using his supernatural powers to search for... something... that his subconscious knew that he was missing...
He was missing the love of his life. As the reborn Prince Endymion of Earth, his heart was searching for the present incarnation of the Princess Serenity of the Moon. In this time, she was reincarnated in the klutzy schoolgirl Tsukino Usagi. They ran into each other (as was inevitable), and after some rather amusing escapades, Usagi discovered that the Tuxedo Kamen who fought beside her when she was SailorMoon was the same man as the Mamoru that irritated her so much when she bumped into him on the bus, or on the sidewalk. They fell deeply in love, he admiring her generous soul and fighting spirit, she relying on his strength and perception. And life straightened out from there.
The love between Mamoru and Usagi is almost tangible, it is so very strong. It is a constant throughout the series, and indeed, the story depends on it. It was because of their love that they died for each other back in the Silver Millenium: he died protecting her, and she killed herself because she could not live without him. The love between them also eventually brought Mamoru back to life when Kunzite's energy blast killed him. (He died trying to protect Usagi. Again. Some things never change.) They balance each other out - Usagi's brightness to Mamoru's darkness; her happy, bubbling charm to his quiet, brooding intensity. One is not complete without the other; they complement each other and create a perfect whole. Mamoru says at one point that she keeps him alive; his foremost goal in life is to protect her.
"Chiba Mamoru" translates to Japanese as "earth protector" - and indeed, he does hold the golden star seed of the Earth, just as Usagi holds the silver star seed of the Moon. He is ever alert for the Earth's welfare, and the welfare of all the senshi -- SailorMoon especially, of course.
He has a special bond with the planet of the Earth - he can feel the darkness within it, and whether it's healthy or not. When he touches things, he can sometimes sense things from them. From Alex Glover's translation of tankoubon #4: "Mamoru's power is called psychometry, and that means he can touch something with his hand and tell everything about it... he can send out aura power from his fingertips and he can use that power to heal or to shock people he touches." Originally, Mamo-chan's powers lie more along the "perception" area more than "action;" however, he gains fighting powers as the series progresses. (Such as Tuxedo la Smoking Bomber... that attack always reminded me of a crashing plane, but that's just me. *smile*)
So. The man has a strong sense of duty -- a desire to do whatever is needed. He's brilliant and obviously hardworking: he's able to put himself through college and own a really nice apartment at the same time. Besides that, his juniors say that he's very smart and good at sports. He's quietly forceful, conscientious, and concerned for others. Best of all, he's very handsome.
Too good to be true, huh?