Complex sentence: Cadmium poisoning from industrial waste in Toyama Prefecture was discovered to be the cause of the extremely painful City in Kumamoto Prefecture were poisoned by methylmercury drained from the chemical factory, known as the "Minamata disease".
Split into simpler sentences: Cadmium poisoning from industrial waste in Toyama Prefecture was discovered to be the cause of the extremely painful. People in Minamata City in Kumamoto Prefecture were poisoned by methylmercury drained from the chemical factory, known as the "Minamata disease".