Truly, I feel moved that you found this for me. The thing that is restored even should it rot... is the human heart.

Is that what you mean to say?

...As someone who had abandoned the Moon,

I thought that my heart had long since grown used to the Earth.

But there's no changing the place that I was raised. It would still be a lie to say that I understand the Earthling heart.

Dispelling the spell of eternity... and taking in all these changes has made me feel that more than ever.

Yet that is why

I can't let it stay rotten!

The answer to your riddle is that which still can't grasp the meaning of this tree.

My own heart.