Tsuboi Ryoutarou

Klein (クライン) is the guild leader of « Fuurinkazan » (風林火山), one of the guilds clearing « Sword Art Online ». He became Kirito's friend after he asked Kirito to show him how to play SAO. His real name is Tsuboi Ryoutarou (壷井遼太郎).

Background
Originally, he was a new player who spotted Kirito as a beta-tester, and requested help. He later rejoined his friends in order to form a guild. He is a stern supporter of Kirito despite the general gaming opinion of beta-testers.

Light Novel Volume 1
Originally, with the appearance of a noble samurai, he is first seen with Kirito teaching him the basics of the game. After being recalled to starting city where Kayaba gives his declaration and his appearance becomes his true appearance. He is with Kirito until he leaves Klein to go to the next village. They are again reunited on the 74th floor with his guild, to have an encounter with an Army platoon. He and Kirito later come to their aid against Gleameyes. They again meet up on the 75th floor for the boss battle, and they fight the « Skullreaper ». He later tells Kirito that it was okay leaving him behind after Akihiko's announcement and renews their friendship.

ALfheim Online
He is reborn as a Salamander warrior. He later helps Kirito obtain Holy Sword Excaliber by setting Freya free who later turns out to be Thor. Later when Skuld appears he asks for her address, to which his whole party is amazed when she actually gives him a contact address.

Mother's Rosario
He appears in the dungeon in level 27 with Kirito and manages to stop the other guild for 3 minutes in order to allow Asuna and the Sleeping Knights to fight that floor's boss.

Sword Art Online

 * Level: 88
 * Main Equipment:
 * 「Karakurenai」 (Katana)
 * Skill Slots: 11
 * Equipped Skills:
 * One Handed Curved Blade - 957
 * Katana - 822
 * Light Metal Equipment - 933
 * Light Shield Equipment - 861
 * Battle Healing - 562
 * Emergency Recovery - 759
 * Searching - 710
 * Listening - 594
 * Extended Weight Limit - 685
 * Fighting Spirit (Hate Skill) - 712
 * Sewing - 366