Item description:

After a 60+ hour grind, I'm sharing my save for this game.
The game is saved at Agumon BLK medal quest.
Speak to Agumon BLK and go to the left hand side. Pick up his property and return it to him.
Then go back to the Agency and turn in the case. This will pop Legendary Medal Collector and the plat a second after.

Note that you can't resign the save at the moment. This is for future reference for when Xploder or other save resigner becomes available.