We have performed two-dimensional two-fluid simulations including finite electron inertial effects to investigate the role of Kelvin-Helmholtz Instability (KHI) on the formation of Low-Latitude Boundary Layer (LLBL). The results from a case in which the magnetic field components along the k-vector of the KHI are anti-parallel across the shear layer indicate that KHI forces magnetic reconnection as its flow compresses the current sheet in its early phase. Reconnection can be triggered even when the Alfven Mach number of the shear (MA) is small (2 < MA < 5: weak KHI). The reconnection process allows the vortex to highly roll-up and thus to form a large scale mixing region. The results imply that the combination of anti-parallel geometry and weak-KHI may play an important role in the formation of the LLBL, which is obtained rather commonly for a realistic LLBL situation under northward IMF.