The commitment to multiplicity and pluriversality challenges design to move beyond singular, stable conceptions of the human. Personal sensing systems offer a rich site for examining this challenge because in mediating the human experience, they constitute the human, although typically as a bounded, rational subject. Building on the critical discourse around sensing technologies, we examine what it might mean to make space for multiplicity in sensing. We articulate “purple zone” as an ontologically ambiguous space emerging from crossing boundaries previously naturalized or deemed fixed, and instantiate it through “EDA purple zone,” marking the threshold of in/visibility in Electrodermal Activity sensing. Through a multi-year process, we developed a real-time biofeedback system that surfaces EDA purple zone. Through a two-week study with 24 participants, we examine encounters with purple zone, instances where the relational human emerges through assemblages, and participants’ strategies for navigating such encounters. We conclude by reflecting on the inherent tensions and possibilities for reconstituting the human in/through personal sensing and engaging ontological multiplicity through design.