Saisuke is a player of The Game. Not much is known about him presently. Kleya Smith is trying to model herself after him. He has a snake special, Seva, and he is very powerful. He doesn't kill anyone and is looking for someone. It is speculated that this someone is a lost love before The Ending.
After defeating the Snowman's group, he went into hiding. He recently surfaced just as Kleya's team was about to enter The Game. Because of his immense popularity, Kleya's team had to wait so that there were enough servers to handle the Watchers load.