This shows basically that Haerpi wasn't always a free boy. the humans which came to the planet Shoa` or "Shadow World" captured some animals and even some of the humanoids called "Usu" For research.
Haerpi was the only one ever of his kind to be captured, as he was young when caught.
Because of the experiments on him, he can change into a human, breath oxygen [but its not native to his planet] and a few other things i can't remember right now.

art/Haerpi/Shoa` © SasukiMimochi