Halloween†Town: Party Time!!

Unknown to humans, a separate world, populated with supernatural creatures exists beside the world of humans. Some people of that world live secretly among humans, for various reasons. This manga is about four teenage boys, Minami, Shiro, Tohru, and Takaya, who all have links to the supernatural world. They pretend to live as ordinary humans, but they work part time to help solve the supernatural incidents in the human world!

(Source: MangaHelpers)