Kou Seiya / Sailor Star Fighter

Seiya has blue eyes and long raven hair falling to the hip, kept in a low ponytail. As the Three Lights' front man he usually wears a red blazer over a navy button shirt with a yellow tie, red trousers, and black shoes, along with a pair of silver crescent-moon earrings he keeps on almost constantly. During concerts he handles a red rose, which he can throw as a weapon, and at Juban High School he wears a uniform distinct from the other boys. His casual looks vary, one notable outfit being a brown leather jacket over a green undershirt with an orange zippered collar, pink trousers, and leather shoes.

Transforming changes his male civilian self into her female guardian identity. As Sailor Star Fighter her height sits between the other two Starlights, and she wears the trio's identical black two-piece of a bikini-style top and hot pants with knee-length boots and elbow-length gloves. She adds a beaded gold tiara, waist belts, and gold star earrings, using light blue as her accent across a belt-like choker and upper-arm straps.

Seiya is markedly more easygoing than the other Starlights, with a mild prankster streak. He warms to Usagi and her friends far more readily than his teammates do, happily flirting with both Usagi and Michiru, and Taiki and Yaten note he is a sore loser. Unlike the other girls, he thinks nothing of killing bugs. His loyalty to Princess Kakyuu is total: he becomes an idol and pours his longing into the group's songs to find her, weeps when she dies, and dreams of a life with her once Earth is safe.

Those feelings run in parallel to what he comes to feel for Usagi. He repeatedly throws himself into danger to protect her, to his teammates' frustration, and even promises to whisk her away across space before taking the promise back, a devotion that defines his arc.

Seiya first crosses paths with Usagi at the airport as Mamoru leaves for America, catching sight of her before walking on. He formally meets her during a shoot where Taiki is filming with an actress, and when the actress is turned into a Phage by Sailor Iron Mouse, the trio transform off-screen into the Starlights. Told by Eternal Sailor Moon not to harm the Phage because the victim is the same person, they watch her heal it, and the Starlights become her rivals; afterward Seiya starts flirting with Usagi.

As the flirting continues the two become friends and go on a date, and Seiya nearly realizes Usagi is Sailor Moon while growing increasingly protective, to the point of being thrown out by Taiki and Yaten. When Sailor Tin Nyanko targets Usagi's star seed, Seiya saves her by hurling a red rose, then furiously transforms and unleashes Star Serious Laser, letting Sailor Moon finish the enemy. He comforts a distraught Usagi with the line "You've still got me," after Mamoru has gone silent. Following Kakyuu's death he joins the guardians against Galaxia and shields Eternal Sailor Moon, only to see her star seed taken. Once Galaxia is healed and Kakyuu revived, Seiya bids Usagi farewell, asks Mamoru to protect her, and departs Earth with the other Starlights to rebuild their homeworld. He transforms with "Fighter Star Power, Make Up" and fights with Star Serious Laser, using the Sailor Change Star and Sailor Star Yell.