This trophy requires having full affinity with Rowen(10 hearts). This can be achieved by completing his character episodes, giving specific answers during skits, linking with him in battle, or by using Friendship Potions. Friendship Potions are rewarded by paying off your debt, or can traded for poker chips at the bar in Duval.
All affinity can be carried over to a new play through using Grade in the shop during New Game +.