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City's record goalscorer Aguero wore sky blue with distinction during his 10-year stint at City, notching 260 goals and winning five Premier League titles at the Etihad Stadium.
The club elected against renewing his contract extension and just days after playing his final game for City - the Champions League final defeat to Chelsea in Porto - Aguero returned to La Liga by signing for Barcelona.
On the day he was presented as a Blaugrana player, Aguero took part in a '90 seconds challenge' where he had to answer as many questions as possible during a video for the club's YouTube channel.
A fan asked Aguero to pick his favourite out of red and blue - Barca's traditional colours and his response has disappointed to City supporters.
After completing the free transfer, Aguero said he was joining the world's biggest club and described the move as "a step forward" in his career.
The 32-year-old's father, meanwhile, ripped into City boss Pep Guardiola and accused him of faking tears during his post-match interview following Aguero's final Premier League appearance for City.
Guardiola paid tribute to Aguero after he came off the bench to score twice in a 5-0 win over Everton.
He called the legendary forward a "special person" and claimed "we cannot replace him" in an emotional speech, but Aguero's father, Leonel del Castillo, claimed it was a case of "crocodile tears".
"I don't believe his tears,", he said, as per the Manchester Evening News.
"For me, he never wanted Kun. He always wants to be the main man and not the players.
"I don't believe [in] Guardiola. He never wanted it [the Champions League trophy], he wants to be the protagonist of all the teams."
Aguero could be set to come up against his former club City sooner than expected, with reports indicating the Premier League champions will play Barcelona in their yearly Joan Gamper trophy fixture at the Nou Camp.