  Recently gamma-ray bursts (GRBs) have been detected at very high-energy (VHE)
gamma-rays by imaging atmospheric Cherenkov telescopes, and a two-component jet
model has often been invoked to explain multiwavelength data. In this work,
multiwavelength afterglow emission from an extremely bright GRB, GRB 221009A,
is examined. The isotropic-equivalent gamma-ray energy of this event is among
the largest, which suggests that similarly to previous VHE GRBs, the jet
opening angle is so small that the collimation-corrected gamma-ray energy is
nominal. Afterglow emission from such a narrow jet decays too rapidly,
especially if the jet propagates into uniform circumburst material. In the
two-component jet model, another wide jet component with a smaller Lorentz
factor dominates late-time afterglow emission, and we show that multiwavelength
data of GRB 221009A can be explained by narrow and wide jets with opening
angles similar to those employed for other VHE GRBs. We also discuss how model
degeneracies can be disentangled with observations.
