Hibiki is a Sekirei, designated as Number 12, who appears in the second season of the anime. She is one half of a pair of twin Sekirei, the other being her sister Hikari. Both are bound to the same Ashikabi, a man named Seo Kaoru. Physically, Hibiki shares a nearly identical appearance with her twin, characterized by brown eyes and long black hair typically styled into two ponytails. A subtle but noted physical distinction between the sisters is that Hibiki has a smaller bust size compared to Hikari. Her attire often consists of form-fitting purple or pink suits, which led to the pair being nicknamed the ones in S&M clothes by other characters early in the series.

In terms of personality, Hibiki stands out as the calm, composed, and mature counterpart to her fiery and short-tempered twin sister, Hikari. She frequently finds herself in the position of having to mediate or suffer through the consequences of Hikari’s aggressive and impulsive attitude. Despite their contrasting temperaments, the bond between the twins is extraordinarily strong, both personally and in combat. They are fully aware that their Ashikabi, Seo, is far from the most powerful or impressive participant in the Sekirei Plan, which has earned them the reputation of being the Sekirei of the Loser Ashikabi. Nevertheless, Hibiki genuinely cares for Seo and is completely loyal to him, willing to defend him against any threat. This loyalty is coupled with a fierce and possessive jealousy; she and Hikari actively prevent Seo from winging or even flirting with any other Sekirei by threatening to, and sometimes actually, striking him with lightning.

Hibiki’s primary motivation, particularly in the early stages of the Sekirei Plan, is to secure victory by targeting unwinged Sekirei, who are generally considered weaker and more vulnerable. Her role in the story is almost always in tandem with Hikari, as the two function as a formidable single unit. They are noted by the powerful Sekirei Homura to be underdogs who possess greater combat expertise than himself, despite their lower overall power level. Hibiki and Hikari act as the primary muscle for their Ashikabi, Seo, engaging in numerous fights throughout the series. They participate in key battles, including confrontations with Musubi, Tsukiumi, and other Sekirei during the Second and Third Stages of the Plan.

The most significant relationship in Hibiki’s life is the triad she forms with her twin sister and her Ashikabi. Her relationship with her sister is one of deep cooperation and contrast, while her bond with Seo is one of devoted, if jealously guarded, affection. As the series progresses, Hibiki’s development is subtle but evident in her growing willingness to admit her feelings for Seo. In contrast to Hikari, who continues to feign indifference, Hibiki becomes more forthright in acknowledging that she cares for their Ashikabi. By the conclusion of the Sekirei Plan’s main conflict, this bond is fully realized; both Hibiki and Hikari are shown to be pregnant with Seo’s children, and each eventually gives birth to two sons.

Hibiki’s notable abilities revolve around the manipulation of electricity and lightning, classifying her as a lightning-type Sekirei. She can generate and discharge bolts of lightning from her hands or fingertips to directly attack her enemies. Her most powerful technique, however, is not one she can perform alone. She and her sister Hikari share a unique Norito, a special chant that unleashes their true power. The Norito is recited together: We're the pledged thunderclap. No disaster will hit our Ashikabi. When activated, this prayer summons a massive, devastating lightning strike that combines their abilities into a single, overwhelming attack. This cooperation technique, sometimes referred to as Karitachi No Ikachuzi or God Song, is their ultimate weapon.