Beniko is the enigmatic proprietor of Zenitendō, a mysterious candy shop that can only be found by those who are fortunate or in genuine need. Her exact age is unknown, but she is depicted as a woman with pure white or gray hair, which she typically styles in a bun, and she wears bright red lipstick along with a traditional kimono adorned with an old coin pattern. She has yellow eyes and speaks in an old-fashioned manner, often ending her sentences with the distinctive verbal tic "gozansu," which adds to her timeless and enigmatic presence.

At her core, Beniko is neither purely benevolent nor malicious; she is a neutral arbiter of choice and consequence. Her primary function is to listen to the troubles of her customers and recommend a specific magical candy or snack perfectly suited to resolve their worries or grant their hidden wishes. She does not force her wares on anyone, and the true power of her confections lies entirely in the hands of the buyer. If the customer follows the instructions and uses the candy correctly, it can bring happiness and solve their problems. However, if they misuse it, ignore her advice, or act from a place of greed or dishonesty, the same candy will bring about misfortune or a cursed result. Beniko simply observes the outcomes, embodying the principle that whether her sweets bring fortune or disaster depends solely on the choices of the people who receive them.

Within the story, Beniko serves as the constant anchor, presiding over the shop while a rotating cast of customers visits her. Her key relationship is with her familiar, a black cat named Sumimaru, who assists her by interpreting her subtle instructions and sometimes guiding lost customers to the shop's door. Beyond her role as a shopkeeper, glimpses into her past reveal a long history. Before establishing Zenitendō, she traveled as a peddler selling solitary cheap sweets, with memories spanning different eras of Japanese history, including the Warring States period, the Edo period, the Taisho period, and the Showa period. These experiences have contributed to her vast knowledge of confections and human nature.

In terms of development, Beniko remains a consistent figure of mystery, though her past is gradually illuminated through stories that explain the origins of specific candies and her eventual meeting with Sumimaru, leading to the construction of the Zenitendō shop. Her notable abilities include an encyclopedic knowledge of magical snacks and an almost supernatural intuition that allows her to select the precise confection to match a customer's deepest internal conflict. She is the guardian of a magical space, and her role is to facilitate a test of character for those lucky enough to find her door.