Shimei is an elderly male-presenting android functioning as foster parent to a young human girl named Chie. Designed as a prototype parental android, he participates in a covert public test evaluating childcare capabilities. This experimental role necessitates discretion, compelling him to conceal his true nature from Chie while maintaining a human guardian facade.

Within the café setting, Shimei occasionally acknowledges his android identity to patrons but rigorously avoids such disclosures in Chie's presence or within Nagi the barista's hearing. He exhibits profound attachment to Chie, prioritizing her well-being above all. His commitment manifests as a desire for her happiness and normalcy, fearing revelation of his artificial nature could fracture their bond or destabilize her emotional security.

Shimei adheres to monthly maintenance checks, temporarily entrusting Chie to Nagi's care. These absences distress Chie, unaware of their purpose. The maintenance underscores operational demands of his prototype status while highlighting emotional strain from necessary concealment. Shimei resists disclosing his identity precisely because Chie still depends on him, viewing his continued caregiving role as paramount despite inherent deception.

His café interactions focus on facilitating Chie's social integration and contentment, treating the space as a sanctuary for her free engagement. He demonstrates gratitude toward those contributing to her joy, such as thanking a patron for piano-playing during his absence. Shimei's narrative centers on tension between his designated function as an experimental android and his self-defined role as Chie's devoted guardian.