  It has been often observed that K\"ahler geometry is essentially a $U(1)$
gauge theory whose field strength is identified with the K\"ahler form. However
it has been pursued neither seriously nor deeply. We argue that this remarkable
connection between the K\"ahler geometry and $U(1)$ gauge theory is a missing
corner in our understanding of quantum gravity. We show that the K\"ahler
geometry can be described by a $U(1)$ gauge theory on a symplectic manifold
with a slight generalization. We derive a natural Poisson algebra associated
with the K\"ahler geometry we have started with. The quantization of the
underlying Poisson algebra leads to a noncommutative $U(1)$ gauge theory which
arguably describes a quantized K\"ahler geometry. The Hilbert space
representation of quantized K\"ahler geometry eventually ends in a
zero-dimensional matrix model. We then play with the zero-dimensional matrix
model to examine how to recover our starting point--K\"ahler geometry--from the
background-independent formulation. The round-trip journey suggests many
remarkable pictures for quantum gravity that will open a new perspective to
resolve the notorious problems in theoretical physics such as the cosmological
constant problem, hierarchy problem, dark energy, dark matter and cosmic
inflation. We also discuss how time emerges to generate a Lorentzian spacetime
in the context of emergent gravity.
