Sayo ran away from yet another family that couldn't deal with him and his outbursts and general emotional problems and he was essentially marked as unadoptable and kind of slipped through the cracks. He got sick of being abandoned.

In game, if he gets in, he's going to be living with Kasen but has a habit of disappearing to his old spots because he was on the streets for so long. He's also still got the fear of everything stable collapsing around him.