c² as Ki-Field Propagation Velocity: A Derivation of E=mc² from the Genki Particle Framework

The interior of a genki particle is void — ku (空). Void is not absence; it is the capacity to be filled. Einstein's equation E=mc² states that mass and energy are equivalent, but does not explain why the conversion factor is precisely c² — the square of the speed of light. Within the Genki Particle framework, we derive c² from first principles as the square of the Ki-field propagation velocity: the speed at which Ma energy (間, ρ_Ma) travels through the continuous mesh of genki particle outer surfaces (気, ki) that constitutes spacetime. Mass is redefined as the quantity of Ma energy stored in the void interior (空, ku) of a matter particle: m = ρ_Ma^(inner) · V_ku / c². When a matter particle undergoes spatial-particle transition (物質粒子の空間粒子化) — the complete outflow of Ma from ku — the stored Ma is released into the Ki mesh at propagation velocity c, yielding E = mc². A Ma conservation law is established: the total Ma energy in the universe (inner + outer) is constant. The neutrino generation efficiency η is defined as the fraction of released Ma that propagates as neutrino residuals rather than photons. These results reframe E=mc² not as an axiom but as a theorem derivable from the structure of void, Ma, and the Ki field.