Yakumo Oomori, also known as 'Yamori' or 'Jason,' is a notorious ghoul in the anime and manga series Tokyo Ghoul. He is infamous for his brutal and sadistic behavior, particularly his torture methods. As a high-ranking member of the Aogiri Tree organization, Oomori plays a significant antagonistic role, especially in the life of the protagonist, Ken Kaneki. His violent nature and psychological manipulation leave a lasting impact on Kaneki’s development, making him one of the most memorable villains in the series.