1) On 3/20, talk to every social link that you have maxed.
2) When asked if you want to go home choose no
3) Go to Junes elevation again, and choose no again when asked if you want to go home.
4) When asked if you'd like to go to the food court for one more time choose yes and initiate an event at the food court.
5) Go to the floodplain and talk to Ryoutaro
6) Go to Velvet Room and talk to Igor, obtain the Orb of View
7) Go back to talk to the staff at the gasoline stand.
You can now enter the hidden dungeon in the food court.