**Viruses vs. a shark-type artificial creature!** To protect humanity from the threat of viruses, the genius scientist Kyou Rouhan created K-1, a therapeutic shark-type bodily sea fish that can swim freely through the human body. However, K-1 has a vicious personality, and is a dangerous being who could become an enemy of humanity… But then, by chance, K-1 combines with a kind-hearted boy who cares for his younger sister!? A marine scifi fantasy about fighting viruses!