Here's what NDLVR said on an older thread:
I can tell you that once you get to where you just need Yumi's last photo (the one of her and Rentaro), if you need to just use up time until it comes, what I do is play pachinko over and over and over until the message comes.So it could be just a case of wasting time in-game before the photo arrives, and what you actually do doesn't matter.
Otherwise, be sure to check your tasklist to see if there's anything else that needs to be done, and try calling and talking to everyone that you can.
