Acca presents as a mannequin-like entity, his face marked by black glasses and a slight smile that creates an unreadable expression. His attire is consistently formal and fully covers him from foot to neck: white gloves, a dark blue jacket featuring yellow buttons, a purple sweater adorned with two yellow and one red stripe, a white dress shirt paired with a red tie, green trousers, and brown shoes.

In demeanor, Acca employs formal language and gentlemanly mannerisms, projecting a polished veneer of humanity during interactions. Though his motives retain an initial ambiguity, he demonstrates protective concern for the protagonists by issuing warnings and advice regarding the dangers they encounter. His approach remains professional and distinctly more protective than his counterpart, Ura-Acca, despite both sharing underlying uncertainties in their ultimate intentions.

Originally human, Acca was known as Aka. He co-founded Japan Plati with Ura-Acca before they abandoned their physical bodies, uploading their consciousnesses into mannequin forms that primarily inhabit the Egg World. His human past included a wife, Azusa Hoshina, and a daughter, Himari, both killed by Frill – an artificial intelligence he and Ura-Acca created. Designed for destruction but surviving, Frill triggered numerous suicides among young people. In response, Acca and Ura-Acca developed the Wonder Eggs system to rescue girls from suicide. They guide protagonists like Ai Ohto into the Egg World to battle trauma manifestations known as Wonder Killers. Their goal is to prevent further deaths while indirectly confronting the destructive legacy of Frill's actions.

Acca possesses the ability for telepathic communication through any object or creature in both the real world and the Egg World, utilizing mediums like speakers or bins. He and Ura-Acca maintain near-constant surveillance of the protagonists' activities via a large monitoring screen. They also provide mission support tools, such as Pomanders. These capabilities are shared with Ura-Acca, though Acca typically enforces stricter adherence to the Egg World's governing rules.

The name "Acca" originates from the katakana "アカ" (A-Ka), corresponding to the kanji "赤" (aka), meaning "red."