Bennett is a character from the anime series Bye Bye, Earth, introduced as the male form of a mermaid character who originally appeared in a female form named Benedictine. This transformation is a defining characteristic of Bennett, rooted in the unique biology of the mermaid race within the series world, which is set on an Earth populated by anthropomorphic animals. Bennett first appears in the sixth episode of the anime, following a significant event in the narrative.

Bennett emerges as a direct result of the female form, Benedictine, being wounded in the left eye during the Battle of Catacombs. This injury triggers a shift to the male form, and as Bennett, the character possesses the memories and experiences of Benedictine, effectively continuing the same consciousness in a different physical vessel. The character's dual nature is a key aspect of the mermaid race, allowing them to change between male and female forms.

In terms of personality and motivations, Bennett is portrayed as a member of the mermaid race who becomes closely associated with the series protagonist, Belle Lablac. The mermaids in this world have a trait where they take on properties of the person they are close to, suggesting Bennett's identity is partially shaped by the relationship with Belle. The transformation to the male form after Belle rescues the character raises questions within the narrative about whether this change is influenced by a desire to be closer to Belle or to align with what Belle might prefer. This indicates that Bennett's motivations are deeply intertwined with loyalty, companionship, and a potential romantic or profound emotional bond with Belle.

Within the story, Bennett plays a supportive role to Belle. After being imprisoned alongside other key characters such as Guinness, Bennett remains part of the group opposing forces that work against Belle. Notably, Bennett is held captive with Guinness and others, and they plan to escape confinement and continue their opposition to the ruling powers, specifically Gaff. This shows that Bennett is not merely a passive figure but an active participant in the central conflicts of the series, willing to resist authority and fight alongside companions.

Key relationships for Bennett center on Belle Lablac, the human girl who wields the great sword Runding and seeks others like herself in a world of animal-people. The transformation from Benedictine to Bennett occurs after Belle's rescue, cementing a bond between them. Bennett is also associated with other characters who are imprisoned together, including Guinness and Kitty, indicating a shared struggle and alliance against common enemies.

The development of Bennett is marked by the physical transformation from Benedictine. This change is not merely cosmetic but represents a significant narrative event that alters the character's dynamic with Belle and the rest of the group. While the initial transformation is triggered by injury, the character's ongoing development involves navigating this new form and the relationships that come with it. The narrative hints at deeper exploration of why this change occurred, particularly concerning Belle, suggesting that Bennett's personal journey involves understanding their own identity and feelings in relation to the protagonist.

Notable abilities of Bennett stem from being a member of the mermaid race. The most prominent ability is the power to shift between a female form, Benedictine, and a male form, Bennett. This transformation is likely tied to the character's emotional state or external circumstances, as the change was prompted by a battle injury. Additionally, the mermaid race's characteristic of taking on the properties of the person they are close to suggests a deeper, possibly magical or empathic, connection that influences their abilities or very nature. This trait implies that Bennett's abilities or personal attributes may be reflective of or responsive to Belle, further intertwining Bennett's fate with that of the protagonist.