Um...

['The planet was once home to creatures known as humans.']

Because...

[Their face scrunch in deep thought, trying to remember a memory that's slipped away, but hangs on the edges of remembrance.

'They divided into three parts--spirit, flesh, and bone.']

Uh...

["Sensei, when Phos's legs wer lost, one third of the gem's embedded memory was lost with them."

The ocean is big and vast...

humans.

Phos gives a frustrated grumble, ruffling their hair and stomping their feet.]

I just do! Well, I know of the word! And now that I'm here and everyone is human, I know what humans are!

[They frown and cross their arms over their chest, looking like a grumpy child.]