"On a planet Earth free of human existence, a new guardian will rise, after a crash landing of a human from another world"
Co is a human explorer, a descendant of people that left their home planet many centuries ago. After having an accident he will end up landing badly on Earth. To save his life after being drowned, the mythical snake "Tren Tren" will convert him into a "Sumpall", the last guardian of water in centuries.
Co in his Sumpall form and also as a human on the left. The other 3 characters are part of his crew and they will go to save him after the crash landing.
