AS says Kepa will be their only mid-season signing.
He has decided not to renew his Athletic contract, which now leaves the ball in Real's court, with the club set to step up their pursuit of the 23-year-old once the window opens on 1 January.
At that point, Kepa - whose Athletic deal expires in June - will be free to hold official talks with another club. His camp has already been made aware that Real's intention is to pay his 20m-euro release clause, but personal terms are still to be agreed.
The Bernabéu outfit are expected to offer the Spain international a six-year contract with an annual salary of around three million euros net.