The Mysterious Sea and the Clouds

Just because of an accident, he fell into a world that was not recognized by the world. "If it is not observed, there is no way to prove its existence." Behind the weird and terrifying events, who is driving all of this. A story, a humanity. He can't escape and can only try his best to find the truth. The truth, is it really the truth? He exists in the future and in the past, but there is no trace of him now.