Era Trees.
They were a type of tree unique to the Four Souls World.
Similar to Sea Star's Adam Tree and Eve Tree.
In other words, there was more than one Era Tree. They were widespread across this planet, and in some places, they even formed forests.
The one at Kagome Shrine was one of them.
"Sacred Tree" was merely the name humans had given it.
However, an Era Tree's abilities were far more miraculous than those of the Adam Tree and Eve Tree.
It possessed the power to send objects, including living beings, through time and space!
Bone-Eater's Well had been made from its timber.
The principle behind this ability was that Era Trees born in and existing across different eras served as nodes.
For example, if this "Sacred Tree" had grown until 2006.
Then it could send people and objects to an Era Tree in the year 2006.
Its starting point was the moment it sprouted into a tree, while its endpoint was the moment it died and vanished.
The timeline between those two points was the range it could transmit things through.
But if one wished to travel to a point in time before it had become a tree.
Then one had to seek out another Era Tree that had been born at the corresponding point in time.
Then pray to the Era Tree Spirit to grant them a Bone-Eater's Well and travel to a desired point in time.
Of course, if the Era Tree Spirit was willing to help, there was no need for Bone-Eater's Well at all.
Because it could create a spacetime tunnel directly.
This answered Kagome's previous doubts regarding the conditions for using Bone-Eater's Well to travel through time.
There were no conditions.
Who could travel and who could not depended entirely on