The Sins Of Ouran
Third Person POV
Greed.
Tamaki Suoh has a best friend, who is equally guilty in unifying the sins. His name is Kyoya Ootori. Kyoya was blinded by Greed and recklessly agreed to help Tamaki with the host club. The thought was innocent enough in the beginning. He just wanted to show his father that he could handle over-taking the family business, but then something changed.
Kyoya got greedy. Once all of the customers piled in and the numbers rose, Kyoya's drive to prove himself to his father got less and less.
Kyoya barely hosted, letting all of the others do the dirty work. And yes, although it was Tamaki's idea to create the club, it was Kyoya who pulled the strings. Kyoya eventually got bored of the usual routine, he wanted, no, needed more customers, and that's when he truly began manipulating Tamaki. Dropping by hints such as cosplay pictures and travel magazines to Tamaki, Kyoya got what he wanted soon enough.
The Shadow King is just an alias for Greed, and Kyoya embraced his sin dead on.