Sergio Leonel Agüero del Castillo (born 2 June 1988 in Quilmes, Buenos Aires Province) is an Argentine footballer who currently plays as a striker for Spanish football team Atlético Madrid and the Argentine national team.
Agüero earned his nickname "Kun" when his grandparents noted that his haircut looked like that of Japanese anime character "Kun Kun."
Sergio Agüero started playing for Argentine First Division Club Independiente, becoming the youngest player to debut in the Argentine First Division at 15 years and 35 days (on 7 July 2003 against Club Atlético San Lorenzo), breaking the record previously established by Diego Maradona in 1976.
In April 2006, it was reported that Atlético de Madrid had "pulled off a stunning transfer coup in the signing of Independiente striker Sergio Agüero." That same day, Independiente denied the reports, but the player himself later told Argentine television "Although I still don't know what's going to happen to me, this could have been my last goal and my last game for Independiente." On 29 May 2006, it was announced that Atlético Madrid had signed the striker for an undisclosed fee, reported to be around €23 million, breaking the club's previous transfer record. In the 2007-08 season, Agüero finished third in scoring in La Liga, behind Dani Güiza and Luís Fabiano, with 20 goals and was runner up in the Trofeo Alfredo di Stéfano award for best player in La Liga.
In the 2008-09 season, Agüero has become a regular goalscorer for Atlético, forming a strong partnership with Uruguayan striker Diego Forlán, also a former Independiente striker. On 1 March 2009, the duo of Diego Forlán and Agüero scored a brace each in a dramatic 4-3 win over league leaders FC Barcelona. Agüero finished in the top ten runners for the Pichichi Trophy while his teammate Forlán won the trophy. Atlético finished fourth in the league, securing a UEFA Champions League spot.