Even in an era when people travel freely through space, there is still a forbidden area for all life and ideals in the universe - black holes. This kind of ruthless star will swallow up everything that comes close to it, whether it is life, matter, or even light. It is a dangerous term that even the most enthusiastic adventurers are unwilling to mention.
Until one day, a man in fiery red clothes announced to the whole universe that there is a miraculous place called the Rainbow Sea deep in the black hole, where gems are everywhere, gold flows in the river, and huge rainbows of tens of thousands of colors span the sky. Anyone who reaches there can realize any wish they have. This declaration ignited the enthusiasm of the whole universe, attracting people from all over the world to follow the man in red and fly into the black hole. In the end, no one could come back. The man in red who disappeared with the adventurers was called the "Red Devil" in disgust by future generations. The Rainbow Sea was also considered the biggest lie in history.
Ten years later, a group of teenagers embarked on a journey...