King of the Mound is a Manga/Manhwa/Manhua in english language, Fantasy series, english chapters have been translated and you can read them here. You are reading chapters on www.mgeko.nl fastest updating comic site. The Summary is

[From the author of Kill the Hero] Through a combination of numerous injuries, a weak frame, and financial difficulties, the protagonist Lee Jinyong gave up on his path to being a baseball athlete and lived as a factory employee instead. One day, the spirit of Kim Jinho, the baseball hero who was hailed as a legend in Korea, as well as Lee Jinyong’s idol who passed away 10 years ago, appeared before him. At the same time, an unknown notice appeared, stating that the ‘Baseball Manager’ would start, and Lee Jinyong gained an ability that gave him the constitution of a pitcher, similar to a game avatar. He returns to the field to become .