Humans always find a way for themselves, and so do elves.
In their pursuit of strength, beauty, and offspring, they chose a compromise.
They delegated the burden of reproduction to the ancient ginkgo tree with whom their souls are connected.
The young elves need only indulge in their pleasures, leaving the trouble of bearing offspring to the ancient tree.
For the ginkgo tree, it's just a matter of giving away a bit more nutrients, as if yielding a few more clusters of fruits, which they are willing to accept.
After all, this is not unpaid labor; to compensate them, the elves continuously elevated the ancient tree's status in the elf-dominated nation.
The result of this transformation is the continuous population growth of the Elf Race, leading the group towards prosperity.
But the division between Blood Elves and Tree Elves marks the path to the group's decline.
