Moonlit Black Cats

Black Cats of the Full Moon (月夜の黒猫団) was a mid-level guild in «Sword Art Online».

Background
Formed with members of a school computer club, and recruited their last guild member within the game. It was destroyed when most of its members were killed in an anti-crystal field and alarm trap, whilst the leader committed suicide after learning of his comrades' death by jumping off the edge of the floor. The sole surviving member refused to join any other guilds until over a year later.

Black Cats of the Full Moon as stated, was a mid-level guild with relatively few members, although all of them barring Kirito knew each other offline. They had hopes for being strong enough to catch up and join the Clearers on the front lines, and with Kirito joining them, believed they stood a chance of catching up.

Except for Keita, who was out bargaining for a new guild home, and Kirito, who somehow survived, everyone in the guild died on June 22, 2023 when they fell into a trap inside a Labyrinth of the 27th Floor.

This led to Kirito refusing to join other guilds for a year.