Kaoru Otoha arrives as a transfer student in Tomoya Mikami's second-year class at Sumisora Academy. She possesses short green hair featuring spiky bangs, hazel tareme-shaped eyes, and a slim, pale build. Her standard outfit is a sailor school uniform, typically paired with a cardigan, necktie, miniskirt, pantyhose, loafers, and she is often seen carrying a bag.

Consistently cheerful and outgoing, Kaoru exhibits articulate social skills and a carefree demeanor. Academically, she excels in language-related subjects but struggles noticeably with mathematics. Watching movies stands as her primary hobby, frequently becoming a topic of her conversations.

Her narrative role shifts significantly across different adaptations and story routes. In one specific storyline, she forms a connection with Tomoya, using film discussions to indirectly address his unresolved grief over a past tragedy. This positions her as a catalyst for his emotional catharsis, helping him process lingering guilt tied to a deceased childhood friend. How effectively she fulfills this role depends entirely on the specific route or adaptation.

Details about her background, including family or life before transferring, remain minimal. Narrative developments involving Kaoru occur primarily within self-contained story routes in the visual novel and its adaptations, such as OVAs. These adaptations often compress her storyline, potentially impacting the depth of her interactions and the resolution of her arc. Tangible recognition within the franchise comes through merchandise like miniature figures.