Tsukasa is the main character of .hack//SIGN.  He is a Wave Master (spell-caster type) that doesn't use magic.  He is mostly a loner, he prefers to be by himself seemingly all the time.  He is cautious but kind, and clumsy with making new friends.

Tsukasa's dilemma is that he cannot logout of "The World".  He encounters a PC (player character) that has hacked it's physical appearence to make it look like and give it the abilities of a cat.  This attracts the attention of the Crimson Knights (self proclaimed police of "The World").  Tsukasa spends most of his time in the Church area.