Relational Emergence of Spacetime: Lorentz Invariance from Two-Way Interactions

We propose a minimal relational framework in which spacetime and Lorentz invariance emerge from completed two-way interactions between systems. Each system defines its proper time as the accumulated count of closed exchange cycles ("both-way handshakes") with its environment, while perceived spatial relations are encoded in relative interaction frequencies. The motivation is to reinterpret the Minkowski spacetime structure from a discrete relational perspective, emphasizing that Lorentz invariance may itself arise from the consistency of two-way interaction counts.