Before Sailor Galaxia came, and before needing to travel to Earth to search for their princess, the Sailor Starlights lived a relatively peaceful life on Kinmoku. Their duty, to protect Princess Kakyuu, was well known and accepted amongst the people on Kinmoku. They did not need to keep their identities secret as the Sailor Senshi living on Earth were required to do, so lived most of their regular life on Kinmoku as Sailor Senshi.
Sailor Star Fighter, the leader of the Starlights, was always the most passionate about protecting the Princess. She was very close to Princess Kakyuu, and loved her very deeply. However, Fighter always felt that there was something more; that in the galaxy there was a star that shined so bright, and so sure, that it could light up the entire galaxy. Fighter believed that she was destined to meet this star, to love this star.
The other two Starlights were content where they were, to be with the Princess, to listen to her telling stories of the Light of Hope, to learn from her, and to sing for her. One of the greatest joys on Kinmoku was to sing- it was believed that a message could reach anyone if it was sent in the form of a song. Sailor Star Fighter was known to most living on Kinmoku for her beautiful and passionate gift of song. Many people wondered exactly who Fighter was singing for. Was it the Princess? Or was she singing to some distant star, a star only heard of in legends? Whoever it was, they were lucky to have such a beautiful voice singing a message of love for them.
Life was perfect, and Kinmoku was so peaceful that the Starlights often felt there was no need for their protection—though they would not rather do anything else. Together, the Starlights and Princess Kakyuu were happy.
Then the Shadow Galactica came, tearing their planet apart searching for its true Star Seeds. Everyone on Kinmoku was being turned into Phages as their Star Seeds were taken. The Starlights felt helpless—for once they were actually needed to protect their planet and their Princess, and yet there was nothing they could do. Attacking the Phages was attacking their own people. Princess Kakyuu was the only one able to heal the Phages and return them to their natural state, however their numbers were increasing so quickly that she could not keep up.
The Starlights could not even protect their Princess. When Sailor Galaxia arrived and realized that the true Star Seeds were within Princess Kakyuu and the Starlights, she attacked Princess Kakyuu. Kakyuu was nearly killed and her Star Seed taken when she chose to flee Kinmoku, hoping for Galaxia to try and follow her, in an attempt to protect the Starlights. Devastated, afraid, and unsure of what to do without their Princess, they chose to follow Kakyuu, leaving anyone who had not been turned into a Phage behind on a dying planet.
Following the light of their Princess, the Starlights made their way to Earth. However, once on Earth, they realized how difficult it would be to find Princess Kakyuu. Earth was so similar to Kinmoku, and yet so different. They found the people on Earth to be more secretive and harsh than anyone on Kinmoku. They quickly realized that they could not stay in their Senshi forms, and so Sailor Star Fighter, Sailor Star Healer, and Sailor Star Maker became Seiya, Yaten and Taiki Kou.
They did notice one thing that Kinmoku had in common with Earth: the love of music. They found music to be playing everywhere they went. People on Earth gathered to watch and listen to idols sing music that they felt they could relate to, that sent a message to them. And so, the Starlights decided that to find their Princess they would do on Earth as they had done on Kinmoku all their lives: send her a message through song. They called themselves the Three Lights, and became instantly famous throughout Japan for their captivating lyrics and extraordinary voices. In their male civilian form, they felt, they would attract the attention of many women, and hopefully reach their Princess.
What felt like ages went by for the Three Lights, and their Princess still had not revealed herself to them. They were all getting frustrated, and bored with the life of an idol on Earth. They were also discouraged that on this planet, without their Princess, the only way to stop a Phage was to end its misery by killing it.
They decided to enroll in high school, since Taiki was eager to gain more knowledge, and Seiya wanted to experience the normal life of a teenager on Earth. Yaten was not as happy with the decision, but since Seiya was the leader, accepted his decision. They chose Juuban High School in Tokyo, despite them not previously living in Tokyo, because Seiya had somehow sensed that he was needed there.
When they arrived at the Tokyo airport, a huge crowd of women surrounded them. Disappointed that Princess Kakyuu still did not appear, and tired of dealing with mobs of people, Seiya broke off from the group in search of a quiet place to reflect on his thoughts. While escaping the crowd, his arm brushed against someone else's arm. As he turned to look at the face of the girl walking past him, he was amazed by her beautiful glow, and was reminded of the star he had always felt he was destined to meet.
Seiya encountered this girl several other times, and was intrigued that she, unlike all the other girls Seiya met, did not recognize him, and did not get excited simply from talking to a famous person. It was the first time since coming to Earth that Seiya felt he could really be himself. Something about this girl reminded him of the light he had dreamed of, and of the Princess he was still searching for.
As we all know, this girl was Usagi Tsukino, and Sailor Moon. After spending time with Usagi at school, and even going on a date with her, Seiya realized that he had fallen in love. He, not yet knowing that she was Sailor Moon, could not understand why a light so pure and so bright was coming from a normal girl on this strange planet. However, he had found why he sensed he was needed at that particular school: he was destined to meet this girl, to feel the warm glow of her light, and to love her.
Even after learning that Usagi was Sailor Moon, Seiya still loved her. He protected her, fought along side her, and even sent messages to her through his singing. I've finally found her, he thought, the bright light I had been searching for my whole life. I was meant to love her. The only problem was that Usagi already had a fiancé. Seiya resented Mamoru from the first time he learned of him, angry with him for making Usagi sad, for not even caring enough to write letters to her when he was so far away.
Am I not good enough? Seiya asked himself this every time Usagi spoke of Mamoru. When she broke into tears after seeing Seiya throw a rose at an enemy, reminding her of Tuxedo Mask, Seiya actually asked Usagi if he was not good enough. Of course, he already knew the answer.
Princess Kakyuu finally revealed herself to the Starlights, and Fighter and the others were ecstatic. Still, Seiya could not keep Usagi out of his mind, even when singing to his Princess. He resolved that he would protect Usagi no matter what, and continue to love her, even knowing that his feelings would never be reciprocated.
After Galaxia finally took Kakyuu's Star Seed, and the Sailor Senshi dedicated to protect the Moon Princess were also killed by Galaxia, Sailor Star Fighter, Sailor Star Maker, and Sailor Star Healer fought alongside Sailor Moon. They had been told by Sailor Uranus and Neptune to protect their Sailor Moon, and so, as Seiya had already resolved to do, they protected her until the very end.
Sailor Moon's love for the world was what freed Galaxia from Chaos' grasps, and her light shone so brightly that the entire galaxy was lit up, just as Sailor Star Fighter had always felt the star she was destined to meet would do. She truly had met and loved the star that she had dreamed about her entire life.
When leaving Earth, finally permanently reunited with Princess Kakyuu, Seiya ordered Mamoru to take good care of Usagi. He then said good-bye to Usagi, saying that he would never forget her. He had finally accepted that his love was an unrequited love, and was satisfied with this.
At least I was finally able to meet her—the star that lit up the entire galaxy, he said to himself with a smile as he and his companions turned into shooting stars and left for their home, Kinmoku.
We will meet again, I know it. I love you, now and forever.