Splatoon/Unavoidable Flying Object

Take the small ramp on the left and furthest from the entrance of Area 5. There is another ramp. Use the ramp and the Inkrail above the ramp. Go up the grate path, then go to the next cube platform, expanding two Sponges. Then, there is a platform with two Inkrails. By using the right-side Inkrail, it'll take Agent 3 to Unavoidable Flying Object. It takes place in a modified version of Blackbelly Skatepark.

Sunken Scroll
Along the western wall of the map on top of a wall. This scroll will be easily seen if you go to the central pillar of the map and take a left. However, the scroll cannot be reached this way. Go to the northern end of the map and take a u-turn around the left wall. There should be an Octosniper waiting for you. Splat the Octosniper, climb the various slopes and shoot the crate sitting atop the wall to find the scroll.