Saint Seiya: Soldiers' Soul

Each character class (Bronze, Silver, Gold, etc.) starts out with 3 Assist Phrase slots and will require you to buy or earn 5 additional slots to reach the total of 8. You can buy slot expansion items from the shop, they cost 80,000 CP each. Provided you grinded in Battle of Gold (Another), you should easily have enough to buy all of the slot expansions required. Alternatively, since the reward for finishing the final battle of the Another Gold God battle mode, is an Assist Phrase character slot for the character that you're using, so you can finish BoG mode 5 times to obtain the slots that way as well. Once you max out the Assist Phrase slots for one character in any class, the trophy will unlock.