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.

Personality
Klein is one of the friendliest people in the series and sets the mood when he's around. He never holds grudges against others and is always ready to lend a helping hand. He cares deeply for his friends and always wants to be by their side fighting alongside them when they are in danger even to the point of getting angry when Kirito was fighting Death Gun, saying he should've converted to GGO as well. He gets angry when people get into situations that can get them killed since he wants to protect as many people as he can.

Klein is a very loyal person which is apparent in his friendship with Kirito. He is very loyal to Kirito despite Kirito usually treating him with coldness. It is later revealed this coldness is due to Kirito feeling guilty for leaving Klein behind at the beginning of SAO. Klein does not care about this however and the two make up as Klein is shown to be the person Kirito relies on the most beside Asuna.

Klein is also a "bachelor" and is shown to try to get together with various women in the series, such as Asuna and Freya. He usually has no luck however, making him somewhat of a comic relief.

Light Novel Volume 1
Originally, with the appearance of a noble samurai, he is first seen with Kirito, being taught 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