He and you were lovers in your previous life. You were reincarnated in modern times and he was in ancient times. He still remembered his past life and he couldn't stay away from you so he brought you back to his time when you were just born.

The bishops of time discovered this and brought you back to the modern world and erased all your memory. When you are on your way to school. Suddenly a man grabbed you

"If they don't let you come to live with me, I'll come to live with you"