Tales of Arise

When you rest at a campsite your party members will sometimes have a speech bubble next to their name which will allow you to have a chat with them before bed. Each time you do, Alphen will bond with them and become closer. You cannot do this again immediately after you've just bonded with a character, so go and do a quest or 2 and rest at a campsit and choose to talk to Shionne again if you can and after a few times you will unlock the achievement as well as a new overdrive art with your new unofficial girlfriend.