Tsuboi Ryoutarou

Klein (クライン) is one of the 10,000 players who were 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) in the web version.

Real Life / Sword Art Online Avatar
Klein wears a headband over his red hair (it is the same one in real life, 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 used red robes and black armor resembling those of a samurai including a katana, along with his guild members.

His facial features include 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 Online.

Background
Originally, he was a new player who spotted Kirito as a beta-tester, and requested help from him. Kirito trained him in the basics of Sword Art Online and was impressed with his progress. Klein later rejoined his friends in order to form a guild. He was a stern supporter of Kirito, despite the general opinions 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 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 trying to get together with various women in the series, such as Asuna and Freya, and even Kirito's sister, who he'd yet to meet. He usually has no luck, however, making him somewhat of a comic relief.

Aincrad Arc


He was first seen posing with his friends while a female news reporter was reporting about Sword Art Online and how only 10,000 copies were sold. Early in the official version of the game, he noticed and identified Kirito as a beta tester, and asked to be taught the basics of fighting. Soon after understanding the basics, he attempted to log out so that he could eat his pizza, but noticed that there was no log out option.

Afterwards, he and Kirito are recalled to the Starting City, where Kayaba Akihiko announces that Sword Art Online has become a death game and a reality, shortly afterwards the avatars of players, including Klein's, are transformed to look like the real bodies of the players.



After the tutorial, Kirito took him to the streets of the city, telling him that they needed to get to the next village together. But Klein refused the offer by saying that his friends must be in the plaza and that he needed to be with them. He suggested that they could all go together, but noticed that Kirito felt worried about the idea, so he dismissed it. Soon they parted ways, with Kirito heading to the next village and Klein returning to the plaza.

They encounter various times throughout the two years in Aincrad due to both of them being in the front lines later on in the game. The first known of such encounters was when Kirito went to the Wolf Plains to do some overnight leveling, as he spent most of the day helping his Guild, the members of the Moonlit Black Cats level up at a fast rate. Another meeting was a few days before Christmas, when they met at the Ant Hill on the 46th Floor, which was the most efficient leveling area at the time. Then again during Christmas, when he tries to convince Kirito not to battle Nicholas The Renegade alone, but he finally lets him go while he and his Guild keep the Divine Dragon Alliance from taking on the boss. When Kirito comes back, he gives the item of revival to Klein, telling him that he must use it within 10 seconds after the person dying.

They are again reunited on the 74th Floor, along with Klein's guild, when they encounter Kirito and Asuna before the arrival 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». After being paralyzed along with most of the front line players, except Kirito, by Heathcliff, he tells the Black Swordsman that he won't forgive him for the first day until Kirito buys him a meal in the real world to make up.

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

Extra Edition
Klein joined Kirito and the others in the «Deep Sea Plunderers» quest in ALO.

Phantom Bullet Arc
Klein is seen watching Kirito battle during the «Bullet of Bullets» tournament at Asuna's rented a 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

Gallery

 * See Klein/Image Gallery

Trivia

 * He was seen on the SAO release day along with the hardcore gamers who were waiting for 3 days in line.
 * His screen name, Klein was derived from the term: Klein bottle (クラインの壺い), based on his real name Tsuboi Ryoutarou.
 * He was one of the 10+ players who had the extra skill «Katana».
 * In the 4-koma Klein is much more prominent and he tends to bug Kirito with messages or calls.
 * In all commercially released media Klein first met Kirito on the first day of the SAO official service start, but in the web version, Klein first met Kirito on September, 2013 (2023 in the Light Novel timeline), three months before the Christmas Event.