Just Because

In the year 1918, a spaceship crashed into Earth. An alien called Xavier was the sole survivor of the crash, he managed to escape the scene and was forced to start life as a human being... Gradually over the years, he manages to successfully assimilate into the human culture, traveling and settling in different parts of the world to avoid suspicions and capture.

99 years later, in the year 2017. Xavier (who is immortal) works as an English Literature professor in MIT is attracted to the "frequency" of an ordinary average-looking girl called Zoey Smith and this is where our story begins...