Izul is a character from the first season of the anime, serving as an antagonist and a member of the Dark Lovers, a group of water demons in service to the primary villain Gaito. As the first antagonist to appear in the series, Izul is introduced in the very first episode, where she attempts to capture the main character Kaito to retrieve the pink pearl he possesses, an act that leads to the protagonist Lucia's first transformation. She continues to serve as an adversary for the mermaid princesses throughout the initial story arc.

In terms of personality, Izul is characterized by a mature and serious demeanor, distinguishing her as the most senior and composed member of the Dark Lovers. She approaches her duties with a high level of dedication, forming strategic plans to capture the mermaid princesses with the ultimate goal of making her master Gaito happy. Despite her stern exterior and occasional arguments with her fellow Dark Lovers, Izul is implied to have a deeper care for them, considering them her good friends. Her loyalty to Gaito is a primary motivating force, driving her actions throughout the first season.

Her role in the story is that of a direct enforcer for Gaito's ambitions. She is often dispatched to confront the mermaid princesses directly, using her powers in battle. One of her most notable contributions to the narrative occurs near the end of the first season, when she performs a significant act of sacrifice. After Gaito's powers are drained, Izul gives up all of her own abilities to restore and heal her master, an act that also reveals her true form to be that of a shark. Beyond the original series, Izul returns in the sequel manga Mermaid Melody Pichi Pichi Pitch Aqua, appearing in the eighth chapter. In this continuation, she is reincarnated and takes on a new role as a music teacher at the school attended by the new protagonist, Lukia.

Izul possesses a range of notable aquatic abilities. She is a water demon, and her powers are intrinsically linked to the presence of water. She has demonstrated the ability to manipulate water to create powerful currents and waves. Her signature attack involves forming the water into fearsome sea dragons that she can control and use to strike her opponents. Her true form, as revealed upon her sacrifice, is a shark. A key vulnerability for Izul, common to many water demons, is the song of a mermaid princess. When exposed to a mermaid's song, the power creates displeasure in her heart, causing her physical pain and disrupting her abilities, which causes her water currents to become calm and her water dragons to dissipate.