You get achievements for choosing each of the 3 types of tea. Every other choice doesn't matter. Once you choose your tea, go right into the room with tables and talk with 3 out of 5 people there. Then sit at your table in the middle. You will get the achievement at some point while talking to the waiter (they didn't pop for me in-game so I'm not sure about the exact moment). You can complete the rest of the story (some 5-10 minutes) but you don't have to if you only want achievements. Just go back to the menu and start over.