Kubo spent last season on-loan with Real Mallorca, his first in the LaLiga, and impressed in a struggling team.
And for his part, Kubo says his future will remain tied to Real Madrid. He told France Football: “My dream has always been to be one of the best players, and I will not stop working to achieve it.
"I've always said my goal was to play for Real Madrid. For this, I work and do my best, even though I don't know what's going to happen. And then I really like being able to play football in one of the best leagues in the world. It shows, doesn't it?"