Tsuboi "Klein" Ryoutarou

Tsuboi Ryoutarou (壷井遼太郎, Tsuboi Ryōtarō?), known as Klein (クライン, Kurain?) in «Sword Art Online» (SAO), «ALfheim Online» (ALO) and «Project Alicization», is a supporting character in the Aincrad Arc and a reoccurring character through the Sword Art Online series. He was one of the 10,000 players who were trapped in Sword Art Online, where he was the guild leader of «Fuurinkazan», one of the clearer guilds. After Sword Art Online was cleared, he began playing ALfheim Online as a Salamander.

In When the Cold Breeze Blows Away, he would be first appeared in during the USRAC War that he is known for to be guild leader of the Fuurinkazan after the Belkan Grey Men framed Vampirina "Vee" Hauntley for ruining his past honorable

Therefore, he and the Fuurinkazan will join the New Central Powers for starting have the advanced skills and the advanced weapons,which he will have his own revenge.