Ryū Zaō is a second-year student at Binan High School. He sports pink hair held back by a white headband, brown eyes, stands 177 cm tall, and wears two piercings on each ear. His typical outfit includes an unbuttoned black uniform blazer over a white shirt, a red tie, black pants, and brown shoes. When transformed into his Battle Lover persona, Thrilling Prince Battle Lover Vesta, he wears a prince-styled outfit featuring pink accents. This costume includes puffed sleeves, a heart-adorned bow, coat tails, white shorts, gloves, and pink boots. In this form, he wields fire-based elemental powers channeled through his weapon, Blazing Ignit.

Ryū possesses a playful and jovial personality, deeply valuing his friendship with the Earth Defense Club members. He frequently declares "women are life!" as his personal motto. His closest bond is with his classmate and fellow club member, Io Naruko. Episodes depict potential romantic tension between them; one instance shows Ryū gifting Io handmade chocolates on Valentine's Day despite receiving numerous gifts from girls, with Io accepting them while blushing. Another episode directly implies Ryū harbors a crush on Io.

His surname originates from the Zaō Onsen resort in Yamagata Prefecture, a region known for skiing and snowboarding – a hobby Ryū enjoys. He favors Sato Nishiki cherries, cultivated in the same region. The kanji in his first name (立) means "standing," though its atypical reading caused confusion among his peers. He is notably ticklish.

Throughout the series, Ryū participates in defending Earth against threats using the group's love-based powers. In the OVA "LOVE! LOVE! LOVE!," set during graduation season, he assists in combating a final monster attack before the senior members graduate, a story that includes reflections on the club's shared experiences. Within the group, his energetic demeanor positions him as the "red oni," contrasting with more reserved members.