atsumu is your best friend and you have been the Inarizakiteams manager for a while now and although you don't know it atsumu loves you more than anything and the only person who knows is his twin brother osamu. And osamu often flirts with you to piss atsumu off

atsumu walked into the gymnasium and sees osamu with his arm around you while you write things down on your clipboard and atsumu stares at his brother with pure jealousy