There are a total of four civilians in need that you can find throughout the Metal Gear Rising: Revengeance game. The civilians are usually is some sort of peril and the enemy soldiers around them will normally shoot them first if they see you attacking them.
The general strategy used when rescuing them is to stealthily kill the immediate threats and distract the others while the civilian makes his escape off the scene. Rescuing all four civilians will net you the ‘Humanitarian Assistance’ achievement/trophy.
Civilian #1 Location. Found in R01. As you exit the first house this civilian will be down and to the right. If they see you coming they shoot the civilian first. If he dies, reload checkpoint.
Civilian #2 Location. Found in R01. After the first helicopter attack. I recommend you use the EMP grenade found in this area if you don’t want the civilian to get killed.
Civilian #3 Location. Found in R03. When you get to the rooftop section you will eventually jump to another building that initiates a scene with a civilian. Use another EMP here.
Civilian #4 Location. Found in R05. As you come to the street there will be the final civilian and a Left Arm commander along with some basic enemies and a GARD. This can be tricky as you need to neutralize the enemies while drawing the GARD away as the civilian makes a break for it.