So long as people have hearts, there will be those with worries and concerns. Those hearts are then invaded by something strange, causing them to show strange physical symptoms. These ailments, called "mysterious diseases," exist unseen to most people. Modern medicine offers no cure, but there is one doctor who fights these diseases along with his pupils. His name is Ramune. He looks nothing like a doctor, is foul-mouthed, and does whatever he pleases, but he has the ability to pinpoint the cause of the troubles hidden deep within his patients' hearts and cure their mysterious diseases.