Undeniable Flying Object is the fifteenth mission in Splatoon's single-player mode, Octo Valley. It takes place in a modified version of the multiplayer stageBluefin Depot.
Upon entering Area 3, Mission 15 is the only kettle found inside the monument-like tower. It is also next to the ramp if players want to escape from that route instead of walking back.
This is the only existing photograph of the legendary Squidbeak Splatoon. The young man folding his arms appears to be the leader. When the picture was taken, the Great Turf War had been raging on for over a year.
Location: In the northeastern corner of the stage, hidden behind a wall. Go through the level normally, preferably sticking to the right side. When you reach the checkpoint right before the grated ramp and walkway, look towards the right behind the wall. There should be a crate containing the scroll.
Armor
Location: Before the Launchpad leading to the UFO, there is a grated walkway. The armor is in a crate at the end.
At the end of Undeniable Flying Object, after the Octostriker has been defeated, some unusual sounds can be heard: an erratic clanking and a faint moan, which are slightly louder towards the edge of the UFO. These sounds were also heard when using Recon to explore Bluefin Depot during a Splatfest. Given Callie's comments on the stage, they may be the result of paranormal happenings or simply the deterioration of old structures.