Aquasteed is crown prince of the neighboring Marinforest Kingdom. While studying abroad in the Lapis Lazuli Kingdom, he witnesses Tiararose's public judgment and impending exile. At this critical moment, he intervenes by proposing marriage to her, diverting the course of the original otome game's narrative. This act establishes him as Tiararose's rescuer and primary romantic interest.

Aquasteed displays intense devotion and possessiveness towards Tiararose. He frequently expresses fervent affection, causing her to blush, and openly compliments her, including remarks about her "sweet" taste. He exhibits jealousy regarding her interactions with others. Their mutual, overt affection results in frequent public displays of clinginess and lovey-dovey behavior, prompting commentary from others about their need for privacy.

His central narrative role involves protecting and supporting Tiararose through political and social challenges, driving the core romantic plot. No alternative love interests or routes exist in the game adaptation. Though a prince with responsibilities and diplomatic engagements, these remain secondary to his romantic function.

Aquasteed maintains his devoted disposition consistently throughout the story arcs across three main volumes, culminating in their ongoing happiness. Bonus stories offer other characters' perspectives but do not alter his canonical relationship with Tiararose or add significant dimensions to his character. He remains the sole love interest in all official media.

His aide, Elliot, assists him professionally, but this relationship does not substantially influence Aquasteed's personal growth or narrative path. Interactions with side characters like Keith or Hartknights primarily serve to underscore his protectiveness of Tiararose, rather than explore his own background or development.