Oboro Yumeshima is a first-year student at Takafuji Private Academy and vice-president of the Food Research Club, known as Shokken. His family owns Umachin, a large confectionery company, matching his personal interest in sweets.

He possesses light green hair styled with short, spiky bangs and cyan-colored eyes featuring a "tareme" (drooping) shape. His build is androgynous, standing 168 cm tall and weighing 50 kg, with a pale complexion and slim frame. He typically wears the Takafuji Academy uniform: a blazer, formal shirt, trousers, dress shoes, and a string ribbon tie. Headphones or pajamas are occasionally part of his attire.

Friendly and teasing, especially toward protagonist Yūki Ōjima, Oboro frequently engages in sexual harassment that annoys Yūki. He uses the pronoun "boku" and is voiced by a female voice actor in all media, enhancing his androgynous portrayal. His hobbies include cosplay and practicing judo.

Across all official media—the original visual novel, PlayStation Portable adaptation, manga serializations, and anime series—Oboro remains a consistent supporting character. His family's confectionery business establishes his wealth, but his character shows no significant development or expanded backstory beyond his established traits and role within Shokken. His interactions primarily serve as comic relief through his persistent teasing of Yūki, with no substantial evolution in his narrative function or personal arc.