Restarting Life: Drowning for the Second Time

An impulsive sophomore picked up an alien nano-life and traveled back to his freshman year of high school, only to find that his new life was a hundred times crueler than he imagined. What's more fatal is that when he tried to correct his mistakes again, two "selves" appeared in the same time and space, and the laws of the universe began to liquidate everything in the form of a black flood.