A thinner paper print card with Yu looking late for school, only just now remembering he left his bag on the bed...  As this is tagged ASCII Media Works, it was likely from one of the Persona Magazines as it's by Shuji Sogabe, but we're unsure.  We'll update when more information comes to the fore.   Good luck making first bell there Yu.
 
~This item qualifies for Lettermail super affordable shipping~!