A friendly player that meets Kirito at the start of the game, who quickly befriends and learns from Kirito. They go their separate ways shortly after when Kirito leaves for another town to power level, while Klein remains behind to help out his less experienced friends. Klein uses a katana to fight and later becomes a leader of his own guild. He regularly meets with Kirito and his friends and occasionally joins them in quests in ALO, especially after the release of the World Seed.
Source from Wikipeida