The 21-year-old centre-back, who had a contract with Barcelona until June 2028, becomes the latest academy product to leave the Catalan club this summer in search of first-team football he was unlikely to find at Camp Nou.
Cortés impressed Hansi Flick during pre-season training with the senior squad, but the sheer depth of competition in central defence made regular minutes an unrealistic prospect for the season ahead.
With Pau Cubarsí, Gerard Martín, Andreas Christensen, Jules Koundé and Eric García all ahead of him in Flick's plans, both club and player concluded that dropping into the reserve side was not the right path for his development. Barcelona have retained a percentage of any future sale as part of the agreement, a mechanism the club has increasingly used when moving on young academy talent.
Cortés made just one senior appearance for Barcelona, coming on against Alavés on 13 May last season, having joined the club's youth ranks in the summer of 2021.
He becomes the latest in a line of young players to leave the club this summer in pursuit of regular football elsewhere, following Tommy Marqués, Héctor Fort, Jofre Torrents and Iñaki Peña out of the Barcelona academy pipeline.
The move to Belgium's Jupiler Pro League offers Cortés a route to consistent senior football that would have been difficult to guarantee in Spain, with Barcelona once again choosing to monetise a departing prospect while safeguarding a financial interest in his future development, should he go on to justify the level of interest he generated during his time in the academy.
Born in Zaragoza, Cortés arrived at Barcelona from Real Zaragoza's youth system and spent a season on loan at CF Damm before establishing himself as a regular at Barcelona Atlético, the club's reserve side.
His departure continues a pattern seen throughout the summer, with the Catalan club consistently opting to sell promising academy graduates for modest fees plus sell-on clauses rather than risk losing them for nothing once their development stalls behind an increasingly crowded first-team squad.