Каїнз

A player who was killed inside a city, which is said to be impossible as there is a protection code preventing players to lose HP inside the city area.

His name is written as Caynz but Yoruko gave a false name Kains to Kirito and Asuna to throw them off. There was a person with the same name who died in a Piercing DoT(damage over time) a year before the inside the area incident. They based their plan with this information and matched the time of death with the time the real Kains died.

He is part of the guild Golden Apple. It got disbanded when their guild leader Griselda died. He and his friend Yoruko suspected that there was someone from the guild who killed the guild leader for the rare item they picked up earlier. They proceeded to do a plan to scare the culprit into confessing in the makeshift grave of the leader by making it that the guild leader rose from the dead and starts to kill the guild members inside the city.