The leader of the Black Organization. Also known as That Person. Karasuma is an influential aristocrat who lives in a golden castle and was presumed to have died 50 years ago.

Rum is the current boss of the Black Organization. He assumes a position of power and leadership, and is involved in their most secret dealings. He is feared even by his own men, who are extremely loyal to him. It is a fact that the important thing in life is to be able to dedicate oneself to something, to embark on a great project, no matter what.. The leader of the Black Organization. Also known as That Person. Karasuma is an influential aristocrat who lives in a golden castle and was presumed to have died 50 years ago. Renya Karasuma is the boss of the Black Organization, and the main antagonist of Detective Conan series. After decades of absence in the organization, he finally made his appearance in file 851, where he attended a meeting with the other members with a new identity as Rum.

Renya Karasuma also known as "RUM" and the "Black Organization Boss", is the main antagonist in the Detective Conan series. He has been given a low profile by Aoyama, with only his hands appearing in a few chapters and episodes alongside his rare spoken lines. He rarely takes actions person. Kuroda was a detective that was hired by Ran to help Kogoro find people who had been stalking her. He saw Ai-Haibara during a case and made her feel uneasy. It is revealed that he is Rum when he overhears Kogoro, Ran, Sonoko, and Conan discussing the Black Organization's involvement in the incident at Beika Central Park

Surce: https://ww4.detectiveconanepisodes.com/detective-conan-episode-12-english-subbed-watch-online/

Haibara is a perceptive woman who is also an excellent judge of character, as shown when she meets Kuroda and immediately concludes that he is not Rum. She has a great insight into the workings of the Black Organization and its agents (particularly Gin), generally taking several minutes to analyze each clue and working out their significance. Karasuma is the leader of the Black Organization and he's the boss in Detective Conan. He appears at the final arc of the series.

Haibara speculated that Rum may be a V.I.P. of the Black Organization and that he once had a significant role in the Organization; she pointed to his exceptional position and excessive trust by Gin, Vodka, Chianti and Korn, who, aside from Gin's example in Conan's first encounter with them, and Korn divulging information about Rum to Sera Masumi at one point, never reveal their missions to anyone else within the Black Organization (serving as evidence for her theory that Gin sees a lot of "his old self" in Shinichi). While Haibara may be partly correct, it was discovered at least one high ranked organization member was suspicious of Rum after Vermouth referred to him as Vaio during her short time on the run from Gin.