The Sailor Starlights were three Sailor Soldiers (Sailor Star Fighter, Sailor Star Maker, and Sailor Star Healer) from a planet called Kinmoku in another Solar System. They protected their princess, Princess Kakyuu, and together ruled over their peaceful planet. Unfortunately, the legendary Sailor Soldier, Sailor Galaxia, arrived at their planet and destroyed it, trying to kill Princess Kakyuu. However Princess Kakyuu escaped from Galaxia and fled to Earth in search of something called the "Light of Hope". With the Light of Hope, Princess Kakyuu would be able to stop Sailor Galaxia from taking over the entire galaxy. The Sailor Starlights followed their princess to Earth, for they thought she could rebuild their planet with her power. There, on Earth, they started to search for her...

  On Earth, the Starlights disguised themselves as male idols (Sailor Star Fighter as Kou Seiya, Healer as Kou Yaten, and Maker as Kou Taiki). They thought this would be the best way to find a woman such as the Princess on Earth. They created a music group called the "Three Lights" and in their songs were secret messages to their Princess. They became very popular and even acted in movies and made a musical. Rei, Makoto, and Minako tell Usagi about them, but ironically it turns out that Ami is the biggest fan of all of them. Eventually, the Three Lights attend the girls' school and they all become friends. The Inner Sailors also discover the Sailor Starlights, but they do not know each others' identities. The Outer Sailors do not trust the Starlights because they are invaders from outside the Solar System and it is the Outers' duty to protect Usagi/Sailor Moon from these invaders.

  The Starlights are extremely strong soldiers. They even seem to match the power of the Outer Soldiers (except Saturn). Later on, all secrets are revealed and the Starlights know the identities of the other Sailor Soldiers and vice versa. However, this breaks the friendship of the Soldiers and the Starlights. Then, finally, the Sailor Starlights find their Princess in ChibiChibi's censer. They all want to leave but Princess Kakyuu says that they must find the Light of Hope first. When Galaxia comes to Earth, she kills Princess Kakyuu by taking her star seed. The Starlights then vow to kill Galaxia out of the vengence for their Princess. However they cannot even injure her. Eventually, the Starlights get so angry that they all attack Galaxia with such force that they break through her barrier and finally injure her. Galaxia is only hurt however, and she continually attacks the Starlights for injuring her. Amazingly the Starlights do not die. After Princess Serenity defeats Chaos, Princess Kakyuu comes back to life and they all return home together.