your eyes tell

Itadori eats the 20th and final finger and with it sukuna is almost at his full strength and is strong enough to take over itadori's body. But but to gain sukuna's full strength he needs his original body, his true form. When he returns to his body him and Sukuna have a battle, in the end sukuna stabs itadori and it results in his death. Then sukuna realised how attached he had grown to itadori now to live the rest of his life in regret...
sorry if the summary is a little misleading in the beginning cuz I ran out of ideas but I might come back to this and make it better! hope you enjoy!