The trophy says "listen to all of the voice lines within the gallery". I have to unlock all the lines, first.
I tried beating every stage in story mode, but I unlocked none of the voices. I beat ambition mode, but I still didn't unlock any charcter lines in the gallery. I maxed out my bond with a few characters, and unlocked the inferior and superior lines for only Dang Ai and Zhang Bao.
How do I unlock all the voice lines for the Vocal Enthusiast trophy?