Ramune, a doctor who acts freely all the time, is badly spoken and doesn't even look like a doctor. He is facing a "mysterious illness" that has no cure. But he is able to discover the cause and cure his patients.

As long as hearts exist inside people, there will always be those who suffer. And then something "strange" enters their mind and causes a strange disease to manifest itself in the body. The illness, which is called a "mystery disease" is unknown to most, but certainly exists. There is a doctor and apprentice who fights the disease, which modern medicine cannot cure. His name is Ramune. He acts freely all the time, is foul-mouthed, and doesn't even look like a doctor. However, once he is confronted with the mysterious disease, he is able to quickly uncover the root cause of his patients' deep-seated distress and cure them. And beyond that.

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.—Crunchyroll

As long as hearts exist inside people, there will always be those who suffer. When something "strange" enters their mind, a strange disease will manifest itself in their body. The illness, which is called a "mystery disease" is unknown to most, but it certainly exists. There is a doctor and an apprentice who can fight the disease, which modern medicine cannot cure. His name is Ramune. He acts freely all the time, is foul-mouthed, and doesn't even look like a doctor. However, once he is confronted with the mysterious disease, he is able to quickly uncover the root cause of his patients' deep-seated distress and cure them.—Official English Site

Mysterious sicknesses have been plaguing various people, causing their bodies to develop unpleasant changes, or discharge strange substances. The symptoms are such that they can't be cured with normal medicine-and that is assuming that the doctors are willing to even believe that such things can happen. Thankfully, Dr. Ramune is ready to cure these maladies, often helping these afflicted individuals discover the equally unpleasant sides of themselves and/or the people around them that they desperately wish to deny. Dr. Ramune: Mysterious Disease Specialist, or Kaibyoui Ramune in Japanese, is a Shounen manga written and illustrated by Aho Toro. The series was initially serialized in Monthly Shounen Sirius magazine from September 2017 to July 2018, before being transferred to Magazine Pocket manga app in August 2018. It received an anime adaptation by Platinum Vision, which premiered on 10 January 2021.—TVTropes