During chapter 7 you will need Saori to join a hostess club to probe some information on ADDC executives. I recommend creating a save before entering the salon as once you leave you are no longer able to access your phone. You will need to do all 5 actions correctly to unlock the achievement.
1. My name is Saori
2. Were you asleep?
3. Hashiki-san!?
4. Give Mika a Sign
5. Get Close to Him