To unlock this Trophy, you'll need to find four posters of real-life model Akina Minami. There are two to find in Act 2 and another two in Act 3. When you find them, go in first person view (hold L1 to ready your gun and press Triangle to look down the sights) and continue to look at them until Snake makes a comment on Akina. There are no in-game rewards for doing this aside from the Trophy. I don't believe you have to do this all in one playthrough, but please do correct me if I'm wrong.Act 21
: Both of the posters in this act are located in the Vista mansion, the area before you fight Laughing Octopus. After entering the building through the front doors (there are two entrances at the front and one at the back of the mansion), look for two paintings next to each other on the wall near the stairs going up. Shoot both of them so they fall off; the poster is behind the larger frame.2
: This poster is in the main bedroom upstairs. Just look at the ceiling above the bed to spot the poster behind the fan.Act 33
: In the first section of the city you start in (Midtown S Sector), ignore the person you're supposed to be tailing and head along the right/east side of the park in the center of this area. Stick to the right wall and continue past the park to the northeast. Eventually you'll come across a small area supported by columns - at the end of this area is the third poster.4
: This poster gave me the most trouble, as it is located in Midtown Central Sector, which you'll usually not go to if you follow the Resistance member. It's hard to give competent directions to find this area, but it does connect to Midtown S Sector. Head northwest from the third poster, go up the small set of stairs on the left, and continue northwest to Midtown Central Sector. Follow the path along and the poster is on a window on the right, near a van.
Here's a screenshot of the map from Act 3, showing the locations of the third and fourth posters: http://imgur.com/lK7DqXu
Below is a YouTube video by heroes0209, which shows the locations of each poster better than I can describe.