  We study the impacts of matter field K\"ahler metric on physical Yukawa
couplings in string compactifications. Since the K\"ahler metric is non-trivial
in general, the kinetic mixing of matter fields opens a new avenue for
realizing a hierarchical structure of physical Yukawa couplings, even when
holomorphic Yukawa couplings have the trivial structure. The hierarchical
Yukawa couplings are demonstrated by couplings of pure untwisted modes on
toroidal orbifolds and their resolutions in the context of heterotic string
theory with standard embedding. Also, we study the hierarchical couplings among
untwisted and twisted modes on resolved orbifolds.
