With enough REP points, talking to one of the Oldhead now will make him get rid of the speakers that were blocking the way into the Mall. Once inside, the BRC need to gather REP points on the way and Vinyl greet them before entering the area with breakable glass which will lead you to the billboard for you to do wallrun and go to the higher level of the mall. There are up to 3 floor levels of this first area but you will meet Vinyl at the 3rd floor (As following her was mandatory to progress) and an Oldhead in green which will open the speaker (Revealed to be a plastic palm tree that you can climb with rail sliding to reach those heaven spots near the rooftop). Here, Vinyl requests you to press the button from the other side of the closed metal door to open the 2nd area of the Mall. The area was actually a warehouse that you can enter by sliding under the gap and tag the switch to open the gate.
Once the gate opened and you entered the 2nd area, Vinyl tells Red to conquer the Mall by beating Dot EXE and promised that she will tell him everything. There are so many tag spots here and floors up to 5 if I counted them right and Shine can be found dancing in the food court in this area. When recruiting Shine, she will tell you the name of the dance she was doing, and you need to do the same dance as her to impress her. After she left, she can be found dancing in the food hall area in the 1st area where the warehouse is, do the same dance as her to impress her for the 2nd time. She will then email you to meet her at EP Record, the red store near the food hall but when you go inside, she wasn't there and instead she was standing behind the stair in the last area with stage (That's actually where the Dot EXE gather). At this point, you can recruit Shine again later after beating all the Dot EXE members because the next area where she is supposed to be is closed. Let's gather some REP points before challenging the Dot EXE.
