Seiya is the ringleader of the Three Lights. She first runs into Usagi at the airport when Mamoru is about to leave to the United States. She then transfers to Juuban Municipal High School, along with Taiki and Yaten. Seiya is a grade 10 student and becomes a star American football player in Usagi's school, and also replaces Haruka Tenou as the star athlete, which causes Haruka to become annoyed. However, the Sailor Senshi becomes suspicious about her true identity. She also develops deep feelings for Usagi.