Hikaru Kudo is a significant supporting character in the anime series E's Otherwise. She is the younger sister of the protagonist, Kai Kudo. Hikaru is depicted as a young girl with a noticeably frail constitution, often seen within the confines of a hospital bed. Her physical appearance includes green hair that reaches her chest and green eyes, and she presents as a child. Her illness is a persistent and critical element of her background, as she has been sickly for a long time and requires constant medical care.

In terms of personality, Hikaru is portrayed as a sweet and gentle child who shares a deep and loving bond with her brother. She is often shown to be in good spirits despite her condition, embodying an innocent and endearing presence that contrasts sharply with the darker and more action-oriented world around her. Her relationship with her brother is the most defining aspect of her character; Kai frequently visits her in the hospital, and his desire to protect her and ensure her well-being is one of his primary driving forces throughout the story. Her vulnerability makes her a powerful emotional anchor for Kai and a symbol of the innocent lives caught in the conflict between psychic individuals and the organizations that seek to control them.

Hikaru's role in the story is less about direct action and more about being a crucial motivation for other characters, particularly her brother. The corporation Ashram, which takes them in, ostensibly provides for her medical treatment, a fact that keeps Kai loyal to the organization for a significant period. However, it is later revealed that Hikaru is not just a passive patient; she is said to possess extraordinarily powerful psychic potential, even greater than that of her brother. Her illness seems to be a barrier that prevents her from fully manifesting or controlling these latent abilities. This hidden power is the true reason for the deep interest that the head of Ashram, Eiji Sagimiya, takes in her, making her a key piece in the larger schemes of the organization.

As a result of her condition, Hikaru has very limited opportunities for active character development or physical movement within the plot. Her development is tied to the revelation of her true nature as a potent esper and the growing threat this poses to her safety. The core conflict surrounding her is not about her own choices, but about whether Kai can rescue her from being used as a tool for Ashram's ultimate goals. This positions her as the central, often fragile, objective around which much of the latter half of the series revolves. Her notable ability is her immense, yet dormant, psychic power, which makes her invaluable to those who wish to exploit espers for world-changing purposes. While she remains a child in need of protection, her latent potential defines her as one of the most significant characters in the narrative.