Onegai Teacher

Today's pick is Onegai Teacher a classic rom-com.

Kei happened to hang out at the lake where Mizuho appears when she gets out of her spaceship. Not giving the situation much further thought, the next day at school he is surprised to recognize the woman, who becomes his new homeroom teacher, as one he had seen at the lake!
But the unreal coincidences continue, when she moves in as his neighbour, ending in Kei being forced to marry Mizuho to preserve her alien identity. But how do you marry an alien when nobody is supposed to know about the marriage, nor about the fact that the woman is both an alien and your teacher?