Why Do They All Say I'm Dead?

When I was a child, I always thought about growing up, but when I grew up, I realized that I couldn't go back to my childhood. So when you grow up, you have to think about time travel, and then Bai Yan really does it. But what the hell is being kissed forcefully at the beginning? And why do they all say I'm dead? This is obviously the first time traveling through time!