  Elastic collisions of solitons generally have a finite phase shift. When the
phase shift has a finitely large value, the two vertices of the
(2+1)-dimensional 2-soliton are significantly separated due to the phase shift,
accompanied by the formation of a local structure connecting the two V-shaped
solitons. We define this local structure as the stem structure. This study
systematically investigates the localized stem structures between two solitons
in the (2+1)-dimensional asymmetric Nizhnik-Novikov-Veselov system. These stem
structures, arising from quasi-resonant collisions between the solitons,
exhibit distinct features of spatial locality and temporal invariance. We
explore two scenarios: one characterized by weakly quasi-resonant collisions
(i.e. $a_{12}\approx 0$), and the other by strongly quasi-resonant collisions
(i.e. $a_{12}\approx +\infty$). Through mathematical analysis, we extract
comprehensive insights into the trajectories, amplitudes, and velocities of the
soliton arms. Furthermore, we discuss the characteristics of the stem
structures, including their length and extreme points. Our findings shed new
light on the interaction between solitons in the (2+1)-dimensional asymmetric
Nizhnik-Novikov-Veselov system.
