This study proposes an axiomatic system for emergent gravity and cosmological unification based on three-state phase transitions of a single neutral quantum field. Specifically addressing the geometric domain established in Paper 2—a single living child universe bubble tangentially invading a Dead Universe Fluid Background—the overall universe must maintain overall charge neutrality for geometric stability, negating hypotheses dominated by multi-polar fields or charged particles, and establishing a minimal foundation dominated by a neutral neutrino quantum field.We convert the phenomenological 'one-body, two-aspects' concept from Paper 1 into strict quantum field theory orthogonal geometry: 'one-body' corresponds to the total amplitude spectrum of the local field envelope, encompassing all entities with mass/energy effects (visible baryonic matter, degenerate dark matter halo, and excited dark energy background); 'two-aspects' represent the vertical phase spectrum (manifested as the dark matter degenerate density field, whose spatial gradient yields emergent gravity) and the horizontal phase spectrum (dynamic dark energy). Four types of neutrinos correspond to three mass eigenstates and potential energy levels: the dead universe fluid background state serves as the sole primordial substrate with an indelible constant zero-point vacuum energy; the excited state is indirectly generated to form dynamic dark energy; the degenerate state forms physical dark matter.We rigorously clarify the boundary between the static vacuum substrate states and the microscopic dynamic excitation wavepackets. On the basis of the background as a non-viscous quantum superfluid continuum, using the first-principle condition of zero mechanical shear modulus, we exclude non-electromagnetic mechanical transverse waves and unify all non-mechanical waves propagating in the background into three geometric sectors: vector curl waves, spinor/longitudinal pulses, and tensor strain waves. Furthermore, we derive the fifth-root expression for the full-band limit speed of light with a rigorous dimensional proof, propose the dynamic mechanism of stellar active pumping transforming into local dark energy, resolving the Hubble Tension and the 120-order-of-magnitude cosmological constant crisis, and present a four-stage birth-and-death cycle for the bubble multiverse alongside an experimental verification roadmap.