We present the flexibility of a human-centered production system called the seru production system (SPS). A theoretical framework for analyzing the flexibility of an SPS is proposed based on the input-process-output (IPO) system view. The enabling effect of workforce configuration on the flexibility of an SPS is explained. The flexibility of SPS is identified to be the capability of an SPS to have inclusiveness and variability. The inclusiveness shows the capability of an SPS to control-variability-with-stability, and variability presents its ability to control-variability-with-variability, which correspond to structural flexibility (SF) and reorganization flexibility (RF), respectively. We reveal that the SPS adopts SF as the main strategy to satisfy most demands and uses RF as an auxiliary means to capture unforeseen demands. In addition, our work reports the strategies for implementing SPS flexibility including structural flexibility strategy, reorganization flexibility strategy, and hybrid flexibility strategy.