Shinji checked and discovered that the world marked on the Feathered Serpent Rudder was the very Shinobi World he lived in!
"Tch."
Shinji spat dismissively.
In other words, to ensure he could capture the Shinobi World, Ryuhei Ubuyashiki had marked it on the Feathered Serpent Rudder long ago.
When he'd read the notes earlier, Shinji had wondered about this.
After all, every world moved chaotically through the void, and sturdy spatial barriers separated them. It was plausible that Ryuhei Ubuyashiki had stumbled across the Shinobi World once by sheer luck, but it made no sense that he could pinpoint it accurately again and again afterward.
After all, Shinji had used the power of the "Light" to teleport to the Hand Demon—the one that had first invaded the Shinobi World from the Demon Slayer World—and slay it at once.
Logically, the moment Shinji killed the Hand Demon, the connection between the two worlds should have been severed.
Only after finding the Feathered Serpent Rudder and confirming that the world marked on it was the Shinobi World did the mystery finally unravel for Shinji.
Then he felt a chill of belated fear.
If he hadn't found this place in time and taken the Feathered Serpent Rudder first, then once the Overlord of Fear devoured the entire Demon Slayer World, the rudder would inevitably have fallen into its hands.
By then, the Overlord of Fear might not even have needed to search for any traces. It could have traveled straight to the Shinobi World using the coordinates marked on the Feathered Serpent Rudder.
"That was close!"
After carefully putting away the Feathered Serpent Rudder, Shinji glanced around the secret chamber again.
Perhaps because the worlds Ryuhei Ubuyashiki had traveled through were generally not very powerful, the spoils here weren't as abundant as Shinji