Seiya thinks that people on earth is very interesting. He points out that
people on earth has so much love and devotion to things they don't know
much about.(He is talking about how the fans treats the Threelights. He
finds it fasinating that the fans could care so much for them eventhough
they don't really know anything about the Threelights)
He is the only person in the Threelights that really
wants to lead a normal life on earth. (Yaten
doesn't really care about anything except to find Princess Fireball.)
Seiya has a thing for Usagi. He really cares and likes her. He even went
out on a date with her. He often gets under her skin... like the time when
he kept the bear chain for himself just so that he could make her mad!
But, at the end, he did gave it to her.(what a sweeet guy! ^_^)
Once he also dressed in a football uniform because he wants to protect
the girls. And, he also hangs out at
Usagi's place so that she wouldn't be lonely (Seiya is soooo nice ^_^)
Seiya also took an attack that was meant for Sailor Moon just so that
she would be alright.
The relationship between Usagi and Seiya is quite complicated. Seiya wants
to let Usagi in on the secret of his love for the princess but Usagi somehow
misunderstood and refused to listen. I think Seiya would have told Usagi
his secret identity prior the unexpected revelation if he had a chance.
Seiya also felt bad that Usagi had to find out his real identity under a
despirate situation. Usagi on the other hand, only sees Seiya as a friend.
What Seiya feels for Usagi is one-sided love.
After knowning that Usagi is Sailor Moon, Seiya felt that he somehow
betrayed her by keeping the secret of his identity. He was the only
one out of the threelights who doesn't mind being a friend of the
planet senshi.
The friendship between Sailor Moon and Sailor Star Fighter is like
Romeo and Juliet. After knowing the real identity of the Three Lights,
the outer senshis opposed Usagi to have any contact with the Starlights
because they don't trust the Starlights and think of them as the enenmy.
On the other hand, Yaten and Taiki also told Seiya not to
be with Usagi because , like the outer senshis being protective of Usagi,
they are trying to protect Seiya. They know that Galaxia is invading earth
and that the planet senshis are in danger, so they don't want Seiya
to get involved because he might get hurt again (Seiya was shot when he
took an attack that was meant for Sailor Moon). Taiki and Yaten are
also afraid that Seiya might spend all his energy trying to
solve the problems happening on planet earth that he
forgets about their only mission -- to find
Princess Fireball.