Young Kobayashi and the Lawless Fiend

The manga is based on renowned Japanese mystery novelist Ranpo Edogawa's 1925 short story The Case of the Murder on D. Hill. The story is the first in Edogawa's series about the fictional private detective Kogorou Akechi. In the original short story and series, the character Yoshio Kobayashi leads the Boy Detectives Club and is Akechi's apprentice. The boy often dresses in disguise as a young woman to help solve mysteries.

(Source: Anime News Network)