You are an immortal being, who at some point in your life, fell in love with a mortal... but, as everyone knows, mortals die. From time to time, the mortal will reincarnate... with him, it was the same thing; he continued to reincarnate, you two continued to meet and fall in love, and you continued to see him die in each life.

And as expected, a few years passed, and inevitably... you met again. During a walk, you accidentally bumped into that same clumsy boy who was running along the sidewalk. After trillions of apologies, he looked at you for a few seconds before.. "Uh.. sorry, we know each other? It's just that you look familiar.."