If you're looking for manga similar to Dorokei, you might like these titles.
"Kindaichi Shonen no Jikenbo 30th" is a commemorative project for the 30th anniversary of the series, featuring Kindaichi and others in high school.
About detective Nanase Gorou, age 25. He works in a private detective agency and solves many variuos, complicated cases. Not only criminal ones, but social ones as well.
After dictatorship and civil war, the South Amercian country, Nascencio, has an ambitious project to make jungle into farming land, which is commissioned to the Japanese company Seshimo. The company's chief, Yuji Seshimo, gets kidnapped while on an inspection tour into the land. Kenichi, a New York noir-style private detective, goes to find his brother...
Kawai is a mysterious man who works in a private detective agency. He calls himself Nobody. His next mission is to go to Russia. Four people are waiting for him and their goal seems to be hijacking a train.
Inspector Oogura Amane has just been reassigned to Investigation Division 6, which is considered a graveyard for police detectives transferred there. Disappointed to discover that her only partner is a slacker by the name of Ebisu Kei, she soon finds out that he has the ability to read the slightest change in facial expressions, or "Tells" as he calls it...
Jotaro Fukamachi is a private detective. Divorced with a woman he can not forget, with whom he had a daughter. He has a reputation for sleuthing, but it is rather stingy and often shows interest. On the other hand, he has principles (sometimes quite caricatured) which it stands. The main one being "always keep a promise," even if the person to whom he made this promise is not of this world. Suddenly, he happens to invest excessively in matters that he won't get any profit.
Tsumaki is a private investigator of the “Aaah Detective Agency” that is obviously listed on the first line of the phone book. He has a great love toward investigation, and aims to solve new cases with his keen and original insight, yet always tends to fail miserably. No wonder he’s pinched to pay his rent… With the support of his colleagues, powerful action, and elaborated costumes, he tries to solve crimes in his original ways!
Kokindaichi Kotaro just recently got accepted to work at the Hanasaki Detective Agency and can’t wait to get real work experience as a Private Investigator. Headed by a young beautiful woman named Hanasaki, her crew of detectives is nothing you would expect. They spend a majority of their times doing nothing and fooling around with no real case to work on. Kotaro tries to learn as much as he can, but the unprofessional work atmosphere makes it really hard. Just when he's about to give up, he sees what amazing potential each member of the agency has.