One of the reasons Urel always
recognizes Keyoko on first sight
is because he gave himself a special
ability to always recognize her.

Even if he can't remember her
upon seeing, hearing, smelling
 or touching her he feels something. 
Sometimes he acts on it and sometimes 
he resists it but is able to note
 there is something strong for her.

 In Mine, Urel is blind and simply
 hears her voice out his window 
and begs his mother for it. 

In Wonder he is on a train and
sees a simple video of her and spends
like all night searching the web until
he finds her.