Manchester City striker Kun Agüero is the attacker Florentino Pérez wants to sign this summer, according to AS. Agüero was on Real's radar when he left Atlético four years ago and he is set to be this summer's main transfer saga, per that same report.
However, it's important to note that AS do not include the potential transfer fee Real Madrid would be willing to pay, so this rumor is possibly just speculation. Nobody knows what Benítez has in mind for this team and while he might think Karim Benzema is not the kind of striker he wants, it wouldn't make much sense to have both Agüero and Benzema on the roster.
Manchester City will not let Agüero leave easily, as he was this season's top scorer in the Premier League and the British club have a big transfer budget. Nonetheless, it's true that they will need to sell some players if they want to make big signings this summer because of FIFA Financial Fair Play regulations.