Mamoru's age:

It's made clear that there is a big age difference between Usagi and Mamoru, but it's never said exactly how much. In the anime it's said that he attends University, so that would make him 18 or 19 at least. In volume 2 of the Manga he flashes his school ID at Usagi while they're on a bus, and it says that he's in 11th grade, so that would make him 16 at least. Usagi's 14 in the beginning, and her 15th birthday is celebrated in SMS, so if she's 14 and he's 16-19 I guess you could say that there's a bit of a difference there.

Mamoru's really long Profile :)

Mamoru is a true gentleman. He has a natural concern for the well being of others, even total strangers. He would do anything to protect the people that he loves.

He was orphaned as a child when the car that he and his parents were driving in went off a cliff. The accident robbed him not only of his parents, but also of his memory.

However, while in the hospital recovering from the accident, he had an encounter with young Usagi, who reached out to him with the simple gift of a rose and relieved some of his anxiety over the loss of a friend. Many long years pass before he encounters her again, and when he does he does not seem to remember their first sweet little meeting...

He lived in an orphanage until he was able to get a job and support himself, but throughout his life was haunted by both a sense of not having an identity, and also by the recurring dream of a plea for help from a mysterious and beautiful princess. He doesn't know who she is, only that she needs his help desperately, and that the two of them once shared a kind of love that few people are ever lucky enough to experience.

One day while walking along the streets of Azabu Juuban he is suddenly pelted in the head with a wadded up ball of paper. Turning, he sees that the pitcher of the pitiful projectile is Usagi. He doesn't remember, but she is the same girl that he met in the hospital years earlier. He advises her to "study harder, dumpling head :)" Sticking her tounge out at him, she snatches her test back, turns on her heel, and flounces away. This is the first of many encounters with her, and with each successive encounter he teases her mercilessly, unaware that she is the girl who will one day become dearer to him than life itself.

At first, Mamoru even seems to be unaware of the fact that he is also Tuxedo Mask. In the anime it seems that he has no control over his transformation. One moment he's walking on the street, the next he is the dashing and impeccably clad superhero who's job it is to rescue Sailor Moon when she's in trouble. He recognizes her strengh, beauty and spunk, and encourages her to be strong. In the manga he tells Usagi that he feels as if he's been "sleepwalking."As Tuxedo Mask he also seeks to acquire the Rainbow Crystals, which the senshi are also after. Because he refuses to cooperate with them in their quest for the crystals, they doubt that he is on their side. However, it will soon become clear to them that he has always been on their side, and indeed, that he always will be.

During a fight with one of the villains, Tuxedo Mask drops a star shaped musical locket. Sailor Moon asks him if it is from the Moon Princess that they are searching for. Does he know her? The answer to both of these questions is actually yes, but Tuxedo Mask doesn't know that yet.

While stuck inside an elevator with Usagi (on his way to a battle with Zoicite for the Rainbow Crystals) he confides to Usagi the secrets of his past, about his parents, his princess, everything. When Zoicite tries to sabotage the elevator with a fireball, Usagi transforms to save herself and Mamoru. Much to his surprise, he finds out that Usagi is the strong, confident, spunky superhero that he is attracted to. But an even greater surprise is yet to come.

After Mamoru reveals to Usagi that he is also Tuxedo Mask, he is impaled through the shoulder with a crystal spear by Zoicite. A tear shed by Sailor Moon as she faces the possible loss of her true love combines with the Rainbow Crystals to form the Ginzuishou (Silver Crystal). Usagi's identity as Princess of the Moon is revealed and it is she who finally answers the questions about Mamoru's past that have mystified him for so long. She helps him to remember that he was once Endymion, Prince of the Earth, and that she was Selenity, Princess of the Moon, the same princess that had been reaching out to him in his dreams all this time.

Together, they remember that they were lovers from a time long ago. When the Moon Kingdom was threatened by evil forces, Prince Endymion fought against them. During the battle Princess Serenity is attacked by the evil Queen Beryl, and her Prince rushes over to defend her. Queen Beryl invites him to join the their side and he refuses. Unwilling to take no for an answer, Beryl snatches him from Princess Serenity's arms with a blast of dark energy. As he is pulled away from her into a vortex of wind, he tells her to "run, just run!" And run she does...

With her home crumbling to dust all around her, and her most valiant warriors already defeated, Princess Serenity makes the descision to run back to the one place where she felt strongest and safest --- back into the arms of her Endymion. Taking a running leap off the balcony of the Moon Palace, she throws herself into the vortex of the wind, calling out for Endymion and reaching desperately for his hand.

They manage to grab on to one another for just a few moments before Beryl hits Prince Endymion with another blast of dark energy. It hits him and spreads like electricity through her too, because they're still clinging to each one other's hands. The last words on their lips in that lifetime are a pained scream of each other's names as the blast pulls them apart and their bodies begin to crumble into moondust. However, Queen Serenity sent them all to the future, so that they would all have a chance at a happy life.

Just after the Prince and Princess are reunited for the first time in a long time, the Prince is snatched away again. He is kidnapped by Queen Beryl ,who succeeds for a time in brainwashing him to become one of her evil minions. For a while Sailor Moon becomes his enemy, but in the final battle against Beryl, Sailor Moon is able to use the power of her love to remind his of what they shared together, and he is once again returned to normal.

However, everybody's memories were erased in the battle against Beryl, so Usagi and Mamoru have again forgotten the great love that they shared. Usagi remembers soon enough, but Mamoru doesn't get his memories back until much later. They return to some of the good natured teasing that they did with each other when the series first started.

In place of Tuxedo Mask, Sailor Moon finds that someone else has arrived to protect her. It's the Moonlight Knight, a mysterious figure swathed in white who looks and sounds just like Mamoru, albeit he is sweeter and more romantic. However he doesn't seem to be Mamoru, because when they turn up in the same room together. Mamoru doesn't recognize him. At the end of the first part of SMR we find out that the Moonlight Knight is actually part of Mamoru's soul. He lost his memories in the battle against Beryl, but deep inside, some part of him always knew that he must protect his true love, the Moon Princess, from the forces of evil. It is for that purpose that the Moonlight Knight was created. After the Doom Tree is healed, the Moonlight Knight fades back into Mamoru's body and his memories are restored.

Sadly, Mamoru and Usagi only have one happy day together on the lake before something --- or should I say someone --- new arrives to test their love. A mysterious pink haired girl falls out of the sky while he and Usagi are kissing. She says that her name is Usagi, and she does resemble Usagi both in appearance and actions. Mamoru gives her the nickname "Chibiusa" (Chibi meaning "little" and Usa being short for "Usagi") A bond forms between them from the start, making Usagi very jealous.

Soon after Chibiusa appears, Mamoru begins having a strange dream. In the dream, he's walking down the aisle with Usagi at their wedding, then all of a sudden his Moon Princess is being torn away from him. In the distance a castle crumbles and an ominous voice warns him that if he and Usagi marry, the world and her are will be in grave danger. The voice is aware of their secret identities as Prince and Princess, something that no one besides him and the other senshi know about. It orders him to stay away from her... or else...

Faced with the possibility of losing the woman he loves and putting the world in danger, Mamoru does what he feels is necessary in order to protect her. He denies his love for her and says he doesn't want to see her anymore. Usagi is shocked and hurt by him suddenly cutting himself off from her, she is unable to understand why he's doing it. The separation is very hard on them both, but Tuxedo Mask is still always there for Sailor Moon when she needs him most.

In their journey to the future, they find out that the sender of the ominous dream is none other than Mamoru himself, or rather, his future self. The dream was a test of their love, designed to find out if they were strong enough to pass through whatever tough times life handed them. They also find out that the mysterious little girl is their daughter, sent from the future to find the Silver Crystal, which she needed to save her home, Crystal Tokyo, the utopian paradise created by the power of Usagi and Mamoru's love.

After saving their daughter after she becomes temporarily evil, and defeating the evil Doom Phantom at the end of SMR, Usagi and Mamoru are happier and stronger than ever. They hit another crisis in SMSS when a shard of Nepherenia's Dream Mirror falls into Mamoru's eye and puts him under her spell. But Usagi never stops believing and fighting for the guy that she loves, and at the end of SMSS the power of her love saves him once again.

Usagi and Mamoru's love has survived all sorts of witches and evil spells, but there is one last great test that they might not be able to survive together: Mamoru's going off to college. Being accepted for a special program at Harvard will separate the two of them for a little more than a year. Usagi doesn't want him to go, but knows that this is a dream come true for him, and that she has to be happy for him.

But he's not leaving her forever. During a tearful goodbye at the airport Mamoru slips a ring on the fourth finger of Usagi's left hand. Do we all know what this means? :) He doesn't propose outright, but after a thousand years and all the love shared between them, does he have to? :) Usagi promises him that she will write him a letter every day, and walks him to his plane. Later we see Mamoru aboard the plane looking at a picture of him, Usagi and Chibiusa, when the plane is hit by a flash of golden light...

After about a month Usagi begins to really worry about Mamoru, because not one of the 30 letters that she's sent him has gotten a reply. They later find out that Mamoru never made it to Harvard.

They finally confront Galaxia, their toughest enemy yet, and find out that Mamoru never made it to Harvard because Galaxia stole his star seed when he was on the plane, hence the flash of golden light. Needless to say Usagi is heartbroken at the news, but she is reunited with her beloved Mamoru after Galaxia is returned to normal and all the star seeds are given back to their owners. Eventually the two of them are married, and they go on to create the paradise of Crystal Tokyo in the 30th century with the amazing power of their eternal love.