Akuma no Akachan(1986)

Pastor Moriyama was sent from the mainland to the remote island of Koiso to work, along with his wife and daughters, Youko and Kasumi. During summer vacation, the Hayasaka family, friends of Pastor Moriyama, visit the island for a vacation. Around that time, Pastor Moriyama is troubled by a lump in his side and decides to see a doctor. An X-ray revealed a fetus that appeared to be an underdeveloped identical twin. Without revealing the details to Pastor Moriyama, the doctor removed the fetus and preserved it as a specimen, but the fetus was alive and managed to escape from the specimen jar. That night, Kasumi had a dream in which a woman dressed in black was breastfeeding a monster-like baby. In the dream, the woman was blowing into a Miyashiro shell—the very one Yoko and she had found while searching for fossils the other day. After the surgery, Pastor Moriyama recovered well and was able to lead Sunday services. However, in the middle of the service, he suddenly started acting like a different person...

It seems this island has a history of devil worship, and now the devil’s messenger has been resurrected. The curtain rises on a tragedy…

(Source: Kaiki Manga no Anagura, translated)