Tsuboi Ryoutarou

Klein (クライン) is one of the 10,000 players trapped in «Sword Art Online» and the guild leader of «Fuurinkazan» (風林火山), one of the clearer guilds. 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).

Real Life / Sword Art Online Avatar
Klein dons a bandana over his red hair (even IRL, it would seem), and his physique seems to be one, or perhaps two, cuts above the average child physique of the SAO universe. During the two years in Aincrad he uses red robes and black armor resembling those of a samurai, along with his guild members.

His facial features includes a thin chin strip, thin eyebrows, a sharp nose, and a pair of gentle eyes.

ALfheim Online Avatar
In ALfheim Online, Klein's appearance is mostly the same as his appearance in Sword Art Online (which is also his real-life appearance), except that his hair is dyed red in ALO. Klein plays as a Salamander in ALfheim.

Background
Originally, he was a new player who spotted Kirito as a beta-tester, and requested help from him. 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 and him being a beta-tester. 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.

Sword Art Online
Originally, with the appearance of a noble samurai, he notice Kirito as a beta tester, and ask to be taught the basics of fighting. Soon after understanding than basics he wanted to log out so he can eat his pizza and notice that there was no log out opinion. Afterwards, he and Kirito are recalled to starting city where Kayaba gives his declaration and his appearance becomes his reality appearance. After the tutorial, Kirito takes him to the streets of the city telling him that they needed to get to the next village together. But Klein informs that his friends must be in the plaza and needed to be with them. He suggest that they could all go together but notice the discomfort of Kirito so he dismisses the idea. Soon they parts ways, with Kirito heading to the village and Klein going back to the plaza.

They encounter various times throughout the two years in Aincrad due to both being in the front lines and are again reunited on the 74th floor with his guild, when they encounter Kirito and Asuna before the arriving of an Army platoon. He and Kirito later come to their aid against «The Gleam Eyes». They again meet up on the 75th floor for the boss battle, and they fight «The Skull Reaper». He later tells Kirito that it was okay leaving him behind after Akihiko's announcement and renews their friendship.



ALfheim Online
Klein is present at Agil's Dicey Cafe to celebrate the «Aincrad Capture Commemorative Party», and later was also present during the unveiling of a content update on ALO, the «Floating Castle Aincrad», which introduced «New Aincrad» to the ALO universe.

Gun Gale Online
Klein is seen watching Kirito battle during the «Bullet of Bullets» tournament at Asuna's rented house at Yggdrasil City. Upon seeing «Death Gun», he reacts saying he knows this person from SAO as one of the members of the red guild, «Laughing Coffin».

Caliber
He is reborn as a Salamander katana-wielding warrior. He later helps Kirito obtain Holy Sword Excaliber by setting Freya, who later turns out to be Thor, free. 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 New Aincrad's 27th floor labyrinth 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)

One Handed Curved Blade Skills

 * Reaver

Trivia

 * He was seen on the SAO release day along with the hardcore gamers who were waiting for 3 days.
 * His screen name, Klein was derived from “Kurain no Tsuboi” (Klein Bottle) based on his real name Tsuboi Ryoutarou.
 * He was one of the 10+ players who had the extra skill «Katana»