Revised version (v2.0) of Koku Universe v3.1. Two corrections from peer review: (1) The speed of light c is redefined as an 'Empirically-Fixed Geometric Invariant' (EFGI): the Koku-face topology establishes that exactly one invariant traversal rate must exist (topological necessity), but the numerical value c = 3x10^8 m/s is empirically determined by physical constants (Planck constant, elementary charge). (2) Falsifiable Prediction 3 (absence of cosmic boundary) is WITHDRAWN as non-falsifiable under Popper's criterion. Two remaining predictions are retained: Prediction 1 (discrete temporal gradient near black holes, testable with 2030s detectors) and Prediction 2 (IceCube neutrino directional coherence, testable with existing data). The core result — E = mc^2 as a conditional geometric theorem — is unchanged.