I'm a BIG supporter of Mamoru and Usagi. Mostly because of the Manga.
In the Manga he does more then throw roses. he's got his own crystal his own attacks.
His relationship with Usagi in it is more mature then the one in the Anime.
Mamoru has something called Pyschometry. It's the power to divine and object or person's history. *it's explained int he 4th manga by Makoto to a kid that attends Mamoru's school.*
Mamoru also has the power to heal or support life into a body. (Ex: In the Anime in the series with the Deathbusters and Pharoh 90. Chibiusa's heart crystal is stolen and she is in fact 'dead' but just like in the manga, Mamoru is keeping her alive. Until Hotaru's spirit can give her crystal back.)
Mamoru also can use an energy attack called' Tuxedo La Smoking bomber'
He can alos use the golden Crystal because it IS his.
Mamoru is connected to The Earth and when he touches the ground he can see who he's looking for.
When the generals- who were his guardians- died, they turn into their name sake stones.
Kunzite, Zoisite, Nephrite and Jadeite. (If you noticed, most of Sailormoon characters are named after Mythology or they're named after minerals/elements and stones.)
He can summon their spirits to help him.
Did I mention that if Usagi ever went with Seiya she would never be queen of Earth. To become a ruler of a place they have to either be in line for the thorne or they have to marry in.
Also, Seiya is a female. In and out of senshi form. Blame the anime creators. Naoko-sama was very ticked at what they had done to her beloved characters.
Seiya is a good friend of Usagi's. May have even had a crush on her. But she is deciated to her princess.
Usagi is not Seiya's princess. Princess Kakyuu is.
Seiya and the other starlights came to earth to look for their princess. They're very much like the Outer senshi when they meet the inners.
They're not looking for a love connection.
The fact that Mamoru is a target *in all the shows and in the manga* as much as Usagi is makes it much his story as hers too.
You just don't put the leading lady with a support character like Seiya. Mamoru is the Leading man and he is an equal of Usagi.
*it's like a yin yang thing.* They're two halfs of a whole.
I have a theory about Chibiusa.
Serenity's mother had pale lavender. No one knows what her father looks like.
He could have had red eyes.
Endymion's parents are a mystery as well. His mother or father could have had pink hair.
On either side of Endymions or Serenitys family that could be a recessant gene.
Chibiusa could just got that one out of one million thing.
<.< highly possible. Though I bet when she grows up her light pink hair will turn white.
Just like Usagi's hair will be when she's queen.