After completing the story for the first time, there is a 'Bonuses' section on the main menu. In this menu is 'Extra Content Shop' and this is where all character/weapon models can be bought using CP.
After buying all models, leave the Extra Content Shop and head to 'Figures'. Once in here, all you need to do is scroll down all the way until you've passed everything. There is an option for a detailed view of each figure but this does not need to be clicked.
After all figures have been scrolled past, you will unlock the trophy.