There are three options for Kubo ahead of the 2021-22 season. The first, the least likely at present, is to remain in the Real Madrid first team and fight for a place with Carlo Ancelotti. The second is to go on loan to Real Sociedad and the third is to do the same, but to go to Mallorca.
Journalist David Alonso reported on this on 'El Transistor', a programme on 'Onda Cero'. He indicated that, previously, there were more teams in the bidding, but that, when Real Madrid asked for a three million euros fee to agree the loan of their young player, many such as Ajax and Alaves withdrew.
Real Sociedad and Mallorca were left and the Japanese player prefers to travel to San Sebastian. He already knows the Balearic Islands, where he played in the 2019-20 season. It is quite likely that he will refuse to return because Imanol Alguacil's side are aiming for more, in principle, in the new season of La Liga.
It is also true that, if he were to sign for Mallorca, Kubo would be more likely to get a lot of playing time. It seems that he has prioritised to see himself in more ambitious scenarios even if he does it in the background or fervently fighting to be one of the leaders of the squad. This comes just after the Olympic Games defeat against Spain.