Imagine Person B of your OTP is in the hospital. They have a horrible fever, and spend most of their time asleep. In the middle of the night, they wake up to find Person A seated next to them, holding their hand. Person B is over joyed, as they haven’t seen Person A in what feels like forever. Person A helps Person B back to sleep, but by the morning Person B is alone again. Only when their fever breaks do they remember that Person A died years ago, and their return was just a fever dream.