Humans are divided up into 4 sections. Fire, earth, water, and air. They do not posses the elemental like powers but have characteristics like the 4 elements.
Like the elements, earth and water go together and wind and fire or the same elements together. It is against the rules to try to be with someone of the opposite element.
80% of the population is born with a specific mark that matches someone elses. The mark appears on the person's 18th birthday. What happens when 4 boys of different elements have the same mark?