Following the news that Thibaut Courtois had suffered a potentially season-ending ACL injury over the summer, Real quickly moved to poach Kepa from Stamford Bridge for the ongoing campaign.
The 29-year-old - who remains the world's most expensive goalkeeper - did not take long to establish himself as Carlo Ancelotti's number one in the absence of Courtois, starting 10 successive La Liga games and three straight Champions League matches.
However, since spending most of November on the sidelines with an adductor injury, Kepa has struggled to win his place back in the team of Andriy Lunin, being benched for clashes with Granada, Real Betis and Villarreal.
Kepa did belatedly demote Lunin back down to the bench against Alaves on December 21, keeping his seventh clean sheet in 15 games as Real won 1-0, and he has made no secret of his desire to remain with Los Blancos.
The former Athletic Bilbao man's contract does not include an option or obligation to buy, though, and according to AS, his hopes of leaving Chelsea for Real permanently are in jeopardy.
Before making the move back to his homeland, Kepa was on Bayern Munich's shortlist to provide backup to the stricken Manuel Neuer, while Real were prioritising the signing of Bono from Sevilla.
However, a move for Bono did not come to fruition due to the Morocco international's impending participation in the African Cup of Nations, and he ended up joining the influx of Saudi Pro League players with Al-Hilal.
Kepa was behind Bono on Real's list of goalkeeping targets, and he has supposedly left a lot to be desired with his performance in the air, which will also harm his prospects of earning a long-term Real deal.
The 29-year-old would also drop back down to second choice once Courtois returns, which would not be until the start of the 2024-25 season, and Lunin still has a contract with Real for another 18 months.
As a result, Kepa could be forced into an unwanted return to Chelsea, with whom he is also under contract until 2025 and has kept 59 clean sheets in 163 games for since joining for a world-record £72m in 2018.
The Spain international managed to win the gloves back from Edouard Mendy during the 2022-23 season, leading to the Senegalese shot-stopper also heading to the Middle East to join Al-Ahli, but Chelsea then reinforced their goalkeeping department with the acquisitions of Robert Sanchez and Dorde Petrovic.
Sanchez is currently out with a knee injury, but Petrovic has proven to be a competent backup, ending up on the winning side in four of his first five starts and crucially saving from Matt Ritchie in the Blues' EFL Cup quarter-final penalty-shootout win over Newcastle United.
Chelsea also have Gabriel Slonina returning from his loan spell at Eupen next year, while Marcus Bettinelli and Lucas Bergstrom are currently at Mauricio Pochettino's disposal.