GAS-TOU NORAINU TANTEIDAN is a Manga/Manhwa/Manhua in (English/Raw) language, Action 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

The setting is London at the end of the 19th century. A young vagrant boy, Louie, meets Sherlock Holmes, a consulting detective who has just opened his own practice, after a murder case. Despite his hatred for Holmes, who does not pay attention to cases involving anything but the upper class, Louie decides to become Holmes' "dog" and work for him in order to gain the ability to protect the homeless children. The splendid tag team of Aosaki Yuugo and Matsubara Toshimitsu presents an underground mystery epic for boys