He is the leader of the guild Black Cats of the Full Moon he and the other members (not including Kirito) are actually computer research club members from the same high school in the real world.
One day, Keita went to buy a little house as their guild home and after he got back Kirito told him all the other members died after they got attacked by monsters. Keita then ran out of the town in Aincrad, and jumped over a fence without hesitation committing suicide by jumping in the endless void.
