Kai Byoui Ramune

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...

(Source: Crunchyroll)