This work is the second technical paper in the UNIFICATION series and expands the Chi Framework by examining the implications of the shared lightlike boundary and associated phase structure.In UNIFICATION 0 and UNIFICATION I, the framework introduced the shared invariant boundary defined by E = pc and ω = kc, together with the boundary parameter χ, the deviation parameter δ, and the phase ratio χϕ. The present paper extends that structural foundation by examining the coupled limiting behavior that emerges as systems approach the lightlike boundary.A central result of this work is the observation that several familiar relativistic quantities evolve together near the boundary. As χ approaches 1, the framework predicts the coupled behavior:δ → 0, γ → ∞, χϕ → ∞, and dτ → 0.This suggests that zero-like and infinity-like behaviors may not be independent extremes, but complementary aspects of the same invariant structural limit.The paper further explores the interpretation of proper time as internal phase evolution and examines how relativistic effects such as energy growth, time dilation, and phase amplification may be viewed as manifestations of a common amplification structure governed by proximity to the boundary.In addition, the work considers whether the shared boundary and its coupled limit structure may admit a future geometric or curvature-based interpretation, potentially connecting the framework to aspects of spacetime curvature and geometric evolution.The present work remains structural and interpretive rather than dynamical. No new equations of motion are introduced, no modifications to established relativity or quantum theory are claimed, and no new empirical predictions are proposed. The contribution of this paper is to clarify how a compact set of structural relations may organize familiar physical behavior in a unified and highly compressed form.This paper motivates future development toward geometric interpretation, field-based formulations, and candidate governing equations within the Chi Framework. Currently Available: UNIFICATION 0 - A Shared Lightlike Boundary for Relativity and Quantum Theory - v1.00 https://doi.org/10.5281/zenodo.19860494 UNIFICATION I - Phase Structure and the Lightlike Boundary - v1.00 https://doi.org/10.5281/zenodo.19862660 UNIFICATION II - Implications of the Lightlike Boundary and Phase Structure - v1.00 https://doi.org/10.5281/zenodo.19863301 UNIFICATION III - Toward a Dynamical Formulation of the Lightlike Boundary Framework - v1.00 https://doi.org/10.5281/zenodo.19895578 UNIFICATION IV - Consequences and Implications of the Chi Framework - v1.00 https://doi.org/10.5281/zenodo.19896296 UNIFICATION V - Concerning the Current Absence of a Governing Equation for the Chi Framework - v1.00 https://doi.org/10.5281/zenodo.19921182 UNIFICATION VI: The Chi Boundary Method and Structural Invariants - v1.00 https://doi.org/10.5281/zenodo.19925550 UNIFICATION VII - A BOUNDED UNIVERSE 0 - Reciprocal Boundary Structure and the Reinterpretation of Zero and Infinity https://doi.org/10.5281/zenodo.20090590 UNIFICATION VIII - A BOUNDED UNIVERSE I - Math of Counting vs a New Zed/Irony Math - v1.01 https://doi.org/10.5281/zenodo.20128424 UNIFICATION IX - A BOUNDED UNIVERSE II - Toward a Bounded Interpretation of Relativistic Extremes - v1.00 https://doi.org/10.5281/zenodo.20160715 UNIFICATION X - A BOUNDED UNIVERSE III - Reciprocal Discernment and the Quantum Boundary - v1.00 https://doi.org/10.5281/zenodo.20171582 UNIFICATION - The Chi Framework - Eight Lessons on the Boundary Between Relativity and Quantum Mechanics - v1.00 https://doi.org/10.5281/zenodo.19863601 A public project archive containing all PDFs in the UNIFICATION series is also available through the Open Science Framework (OSF): UNIFICATION SERIES: https://osf.io/mpvgj/files/osfstorage/