Born in Azpeitia, Gipuzkoa, Aranburu made his professional debuts aged 18, in the last round of 1996–97 against CD Logroñés, courtesy of manager Javier Irureta. From his fourth season onwards he became a full member of the main squad, being essential as the Basques finished second in La Liga in 2002–03 by contributing with 34 games and two goals. Aranburu was seriously injured during 2005–06, and returned to major action only to see Real be relegated the following year, the first time in four decades. He continued to be an important first-team member during the second division campaigns, appearing in 35 matches in 2009–10 to help the Txuriurdin return to the top level after three years. In 2010–11, Aranburu was once again first-choice, partnering Diego Rivas in central defensive midfield in most of the games. He equalled a career-best five goals, including two in a 4–0 away win against Getafe CF – he only played five minutes in the game– and the all-important last-minute winner at home against Real Zaragoza in the 36th round (2–1), as the side narrowly retained their division status.

Segunda División: 2009–10