Twelve warriors from two powerful clans of the EXO planet are sent to Earth for an important mission - one that will decide the future of both worlds. Although one in their goal, differing views and a centuries-long battle between their clans make it difficult for them to work together. As they face challenges on Earth, they discover the truth about their mission. Forbidden relationships begin, friendships end, tension rises and feelings wither as they continue their journey. Along the way, they realize their true missions in life and gain happiness as these are ultimately fulfilled.