Aoi Mashiro is a high school student who relocated from Omiya in Saitama to Kyoto for her studies. This move strained her relationships, leading to a breakup with her boyfriend Katsumi, who subsequently began dating her former best friend Sanae. These personal difficulties prompted her initial visit to the antique shop Kura in Kyoto's Teramachi Sanjou shopping district, intending to sell inherited paintings to fund a trip back to confront them. Instead of completing the sale, she accepted a part-time position after encountering Kiyotaka Yagashira, the shop owner's grandson.

She has shoulder-length chestnut brown hair, typically styled with a back braid and forehead-framing bangs. Her amber or golden brown eyes are often noted alongside her rosy cheeks.

Personality-wise, she is honest, straightforward, and emotionally transparent, laying her feelings bare even when vulnerable—a trait others find disarming for its tension-alleviating effect. Yet she remains modest, gullible, and easily flustered when teased. This gullibility and openness occasionally lead others to jest about her being easy to manipulate.

At Kura, she assists with shop operations while learning antique appraisal from Kiyotaka, who values her innate intuition for discerning authenticity and true value. This mentorship casts her as a Watson-like figure in solving cases involving art forgeries, counterfeit antiques, and artifact-linked personal histories. Through these experiences, she hones observational skills and antique knowledge, helping resolve emotionally or historically significant mysteries.

Her background involves adjusting to Kyoto life, balancing part-time work, and navigating evolving dynamics with those around her—including a rivalry between Kiyotaka and novice actor Akihito Kajiwara, who compete for her affections.