Tantei Aoneko探偵青猫; Detective Bluecat

From Fifay.net: It was the roaring 20's, and the country was Japan. Bluecat, or Aoneko, is a debonaire aristocrat with too much money and leisure time. Along with his servant boy Tigerman, he dabbles in private detective work much to the chagrin of the real police detective Mr. Bee-Prince (Hachiouji). Bluecat is handsome--and yes, he knows it--witty, polite, and popular among the rich. However, his deviant libido, as well as his own attractive nature, often land him in danger. Note: This manga contains relationships between adoptive father and son, and molestation.