He is the guy that,
when I am scared, he will be by my side
when I need him, he will try his best to be there;
even when he's really tired or when he's sleeping,
he would wake up, get out from the bed and guide me through the dark at night just because I told him that I was scared to go there alone.
This, makes him "the" guy.
People might think that a guy waking up in the middle of the night and accompany a girl to the kitchen isn't that great of a deal.
But to me, other than my dad, he is the second man who would do that for me.