In Yakuza 4 you can knock people onto the ground if you run into them. Find a busy intersection such as outside Millennium Tower and run into people at a full run. From my experience only male NPCs fall over and the old guys and males with briefcases are particularly susceptible. It's also best to try to hit them from the rear. Most of the time they will flinch which won't count, they have to physically fall to the ground for it to count.