It looks like Aguero is really mad that Messi has officially left the club. He has come to Barcelona for Messi. And now it looks like Aguero wants to leave also.
Aguero is a professional football player, he won't leave Barcelona just because of Messi leaving. Also, I am sure the biggest reason why he came to Barcelona isn't about Messi. He must know Barcelona is a better place to get more titles and probably to have a new experience there. Since Barcelona is one of the biggest clubs in the world that already won various trophies, all players must expect to be a part of that club. Now, Aguero has the chance to shine in Barcelona, even without Messi. I believe he won't waste the chance to be a Barcelona superstar.
Yeah,we understand Aguero is in Barca to make tittles,but one of his motivating factor to come to Barca was the fact that he was going to play with Messi,the world best player.And now that Messi is no longer in the team,it would be even hard for Barca to even win a major tittle,because the team was built around Messi.