This achievement is earned for finding optional photo #4. If missed on the first run, you can "Play Episodes" and select specific parts of the Episode in order to find the missing optional photos through collectibles mode
. The following collectible is described and can be seen below:
] - Optional Photo #4
Once you make it outside the dormitories, walk to the far end of the area where you'll notice a girl on a bench in front of a tree. To the side of the tree, you'll spot a squirrel which you'll need to take a photo of.
Collecting all 10 photos will also reward you with the following achievement: