Schematic picture of orbital calculation of pebbles. The starting point of pebbles is (x_s, |y_s| = 40 R_Hill, z_s). The x- and z-coordinates of the starting point of pebbles, x_s and z_s, are parameters. The green circle area represents the hydrodynamical simulation domain with radius r_out. We used the gas velocity obtained from the hydrodynamical simulation to calculate the gas drag force acting on the pebble within r_out. Outside r_out, the gas velocity is assumed to be the speed of the sub-Keplerian shear flow.