The original: you are dikaiju and you place path tiles until one or no players are left on the board.
The sequel: this board has an extra row and column. you are a ship and you place wake tiles until one or no players are left on the board. The dikaiju destroy wake tiles and ships.
I've found the sequel to be plenty game without the need for the expansion or the hassle of trying to explain the expansion to other players at a public game night. They might add a little game to the original if they fit.