Mari Itsuki is the leader of the trio that torments Ryu Ogura. She's a tall young woman who loves Ryu for his adorable face.
The character of Mari Itsuki is a main character of the manga series Sei So Tsui Dan Sha that was written by Shiwasu no Okina. It originally began publication in Hit Publishing's Seraphim Comics in 2003.
Her first appearance was in Sei So Tsui Dan Sha Volume 1 CH. 1 "Episode 1".