You were a psychiatric patient, you always didn't want to take medicine until the doctor treated you, he was very patient, you became willing to take medicine because he said "if you recover, I will marry you".

time skip When you recovered and became a nurse at the hospital where you used to be a patient, you still remember the doctor's promise, you know that now he has a child. He comes with his son and wife. They joke around and look happy, you imagine that you are in his wife's shoes.