Kurama Ranko is the leader of the Kurama-gumi, an illegal casino owner and member of Kakerou.

(Source: Usogui Wiki)

There are gamblers out there who even bet their lives as ante. But to secure the integrity of these life-threatening gambles, a violent and powerful organization by the name of "Kakerou" referees these games as a neutral party. Follow Baku Madarame a.k.a. Usogui (The Lie Eater) as he gambles against maniacal opponents at games&mdash;such as Escape the Abandoned Building, Old Maid, and Hangman&mdash;to ultimately "out-gamble" and control the neutral organization of Kakerou itself.

Usokui is a manga one-shot created by Sako Toshio, in 2005, for Weekly Young Jump's 48th Manga Grand Prix competition. It won an honorable mention and was later published in the 48th issue of the magazine, that same year. The one-shot serves as a prototype for what eventually became Usogui.
 
Note: Republished in split-up sections as side stories for volumes 12-15 of Usogui as Igyou Tobakusha Usokui.

Ranko Kurama