The Monstrous Gui is a Manga/Manhwa/Manhua in english language, Drama 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

Childhood friends Seunghwan, Dohee and Sangmin continue their cherished friendship even when they entered high school. However, they’re friend Sangmin disappeared due to the appearance of grosteque creatures called Goei (Gui)… As they search for their friend Sangmin, they found a few secrets… Will Seunghwan be able to recover his childhood friend?