There is no widely recognized media property, game, or book series titled Ninja Proxy
But she had never seen his face.
While not a ninja, Mao Mao is an apothecary who serves as a proxy (a food taster/poison detective) for the high-ranking Jinshi. Their relationship is the perfect modern translation of the trope: He is powerful but vulnerable; she is low-status but intellectually dangerous. Their exclusivity is defined by unspoken pacts and the inability to confess due to court politics. It proves the trope works even without shurikens. ninja proxy xnxx sex exclusive