Read The Road of Karma hentai manga on hentaidexy.
summary for The Road of Karma :
Inhan Kang, a happy-go-lucky librarian, one day receives bad news, that he has cancer. So he starts trying to get medical treatment, when that doesn’t work, he starts praying, when that doesn’t work, he turns to Chi/Ki techniques. His last try actually works, and his cancer starts stagnating, he continues doing it, until one day, when he gets transported to another world. There he has to start learning how to survive.