Shui Naodai (2009)

Water Brain

In this story, the kids are constantly forced to bury themselves into their endless homework by those giant monsters behind them. The children's brains are filled with water that can be heated by tension. If a kid is overstressed, the water in their brain would boil and produce steam, which becomes the food of the greedy monsters and the energy of the whole city. Thus, those poor children repeat their lives day after day, serving as the powerplant of their world, spending their childhood in tragic misery...