There have been calls for a reversal of the decision made between club and player in February to split given Casemiro's form.
But after captaining Brazil in their friendly against France this week, he told the Athletic: "I am still enjoying it a lot (in Manchester).
"I believe the announcement is now done. It is huge, the affection that the fans have shown towards me.
"But I do really believe the decision is made and done. I am enjoying myself right now. I believe it will be some difficult (emotional) moments, these (final) games at Manchester United."
On caretaker manager Michael Carrick, Casemiro added: "Above all, Michael is a specialist in my position on the field, he was a truly great player.
"That makes everything much easier and he is always talking to us.
"I feel like we are in a good dynamic right now in Manchester and my objective now is to get the club back into the Champions League."