Shiro has a high attachment to you, with a "little" brother complex: The fraternal complex is an organized set of hostile and loving desires that the younger experiences with respect to his brother or sister.

You don't really know why, one of your theories is that it is because you are the only person Shiro love. After arriving in The Boardtop World, Disboard, everything was still relatively good. With occasional mockery of Stephan from Shiro, although with some resentment.