The Morning Doctor and the Evening Witch is a Manga/Manhwa/Manhua in english language, Demons series, english chapters have been translated and you can read them here. You are reading chapters on www.mgeko.cc fastest updating comic site. The Summary is

Kou, a boy, visits Hakone to cure a special illness. He arrives at a remote clinic. Despite the spacious clinic with a swimming pool and other facilities, a female doctor lives there alone. Her name is Babel. The female doctor diagnoses that Kou's treatment requires contact with the seductive opposite s3x. This is the story of a daily medical examination between an innocent boy and a bewitching female doctor, which can never be told to others.