Ryuu has pink hair kept in place by a white headband, with the back spiking outward and a loose section falling over the left side of his head, along with a single strand that hangs over his forehead. He has brown eyes and is the second shortest member of the Earth Defense Club. Notably, Ryuu has two piercings in each ear, making him the only member of the group with visible piercings.

His Binan High School uniform consists of long black trousers, a white shirt tucked beneath a black blazer worn unbuttoned, a red tie, and brown shoes.

When transformed into the Thrilling Prince, Battle Lover Vesta, Ryuu wears a flamboyant, prince-inspired costume. His outfit includes a white jacket with puffed sleeves and pink upturned cuffs, extending into six coat tails lined with pink fabric. A pink bow rests beneath his collar, decorated with a winged, heart-shaped jewel. A frilled white undershirt peeks from beneath his jacket, paired with white silk gloves, white shorts trimmed in pink, and pink boots with brown soles, each accented with a decorative buckle. The design emphasizes his role as the fiery and passionate Battle Lover Vesta.

Ryuu is portrayed as a playful and outgoing character, often bringing an energetic and lighthearted dynamic to the Earth Defense Club. His jovial disposition makes him approachable, and he is generally on good terms with all of his teammates. Ryuu values friendship deeply, and his sociable nature allows him to act as a bridge between the more contrasting personalities within the group.

As revealed in Episode 1, Ryuu lives by the motto “Women are life!”, highlighting his flirtatious tendencies and interest in romance. While this aspect of his personality is sometimes exaggerated for comedic effect, it contributes to his role as the most flamboyant and extroverted member of the Battle Lovers.

Ryuu Zaō is introduced as a second-year student at Binan High School and one of the five original members of the Earth Defense Club. He is known for his outgoing personality and distinctive appearance, often standing out among his peers with his piercings and headband.

His backstory highlights his strong friendship with Io Naruko, his classmate and closest companion in the series. Although the two initially clashed due to their contrasting views Ryuu’s focus on dating and Io’s fixation on money their rivalry softened over time, and they became inseparable partners. Their bond is frequently depicted as one of the central dynamics within the Defense Club.

Ryuu becomes involved with the Earth Defense Club after encountering the pink wombat-like creature, who grants him and his friends the ability to transform into the Battle Lovers. Assigned the element of fire, he takes on the persona of Battle Lover Vesta, embodying his fiery, passionate energy in combat. While he may appear frivolous or flirtatious at times, Ryuu consistently proves himself a loyal teammate and an essential part of the group’s unity.

Io Naruko
Ryuu’s closest bond is with Io Naruko, his classmate and fellow member of the Earth Defense Club. Their friendship is emphasized from the first episode, where Io is shown to be protective of him, even delaying his participation in a battle until Ryuu is placed in danger. Their dynamic is often portrayed with humorous or romantic undertones, particularly during Episode 7, when Ryuu is accused of “liking” Io after a misunderstanding involving Io’s toothbrush. Although Ryuu frequently declares that “women are life,” his behavior around Io suggests a deeper connection.

Season 2 expands on their relationship, providing flashbacks to their first meeting. Initially, the two disliked each other Io dismissed dating as “a poor investment,” while Ryuu criticized Io’s obsession with money as shallow. Their rivalry softened during an incident at the Kurotama bathhouse, where an accidental mishap led them to reconcile and begin forming a bond. They later discovered that Yumoto had burned their school jackets while ironing and replaced them with matching emblems, which they pretended to dislike but secretly cherished.

Their interactions often highlight mutual affection disguised by playful denial. In Episode 9 of Season 2, Ryuu gives Io chocolates for Valentine’s Day. Although Io feigns indifference, he blushes as he accepts the gift, reinforcing the suggestion that their relationship contains romantic undertones. Despite their differences, Ryuu and Io consistently complement one another, making their friendship one of the most prominent in the series.

Akoya Gero
Ryuu and Akoya Gero have a tense relationship, stemming from a competition during their first year. Both tied for third place in the school’s “Prettiest Boys” contest, which led to lingering resentment. Akoya has been shown glaring at Ryuu on multiple occasions, suggesting that the rivalry remains unresolved.

The given name Ryuu (立) uses the kanji for “standing.” Despite being written this way, the kanji is not normally read as “Ryuu,” a fact humorously addressed in one of the series’ audio dramas where the characters discuss the peculiar readings of their names.

His surname Zaō (蔵王) combines zō/za (蔵), meaning “warehouse” or “storehouse,” and ō (王), meaning “king,” “prince,” or “monarch.” The name also references Zaō Onsen, a famous hot spring and ski resort located in Yamagata Prefecture, Japan. Known both as a winter sports destination and a traditional hot spring village, Zaō Onsen is one of the many real-world spa resorts that inspired the surnames of the Binan Koukou Chikyuu Bouei-bu LOVE! characters.