If like me, you finished the game with max synergy level, all KK investigation notes and all spirits, you’ll be missing 20 skill points to finish this trophy. In chapter 5, BEFORE YOU ENTER TOKYO TOWER, you’ll battle a boss. After finishing this you’ll be back in the area before the tower, look to your left and there’s a shop stall with two vending machines outside. Enter this building and on your left on a table is a hidden KK Investigation note “The Hyakki Yako”. This should get you the last 20 points you’re after.