Demand Killer is a Manga/Manhwa/Manhua in english language, Action 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

The killer, Cong Zhong Feng has always despised those who fail to keep their word, especially those first parties who keep changing their requests! When he meets a bald young painter, Cong Zhong Feng agrees to avenge her for free. Who would have expected that along the way, they would meet “a set of Matryoshka”, who is the ultimate target?