Frisky Business (EP)

Lucy is the least forward of all the girls in the game. You only need to go on a date with her but don't not need to get frisky. In chapter 8, when you are asked which girl you want to check up on, choose Lucy. The conversation will lead you to asking her to come over for dinner. When she arrives at your apartment, the trophy will unlock.

If you are following the Roadmap, this trophy is part of Run #1. The Walkthrough for this can be found here.