  Using the exact WKB analysis of the higher-order differential equations, we
analyze the asymmetry in dynamical particle production of a complex scalar
field. The solution requires the Stokes phenomena of the fourth-order
differential equation. We found that the interference of different types of the
Stokes phenomena causes matter-antimatter asymmetry. We also showed a specific
example where asymmetry is forbidden in the exact calculation, but a false
asymmetry appears in the perturbative expansion.
