The Japan international has a deal with La Real to 2029, but admits coach Imanol Alguacil's decision to leave at the end of the season has given him pause for thought.
Kubo told Movistar: "At the moment, I have a contract and my idea is to stay at Real Sociedad and for Real Sociedad to improve, but, just like the manager, you never know.
"But right now I have a contract and I'm still at Real Sociedad."
Meanwhile, on Imanol, he added: "He's the same as always, trying to make the team better, as he always does. Do I understand him? Yes, who wouldn't!
"There are other people leaving the club, like the doctor, some more certainly. Those decisions depend on each individual and we have to respect them. We have to thank him for his work. The club will continue with another coach."