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
The guild was formed with members of a school computer club. Kirito was later recruited by them in-game, lying about his true level and claiming to be about as strong as the members of the Black Cats of the Full Moon.

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 22nd, 2023 when they accidentally triggered a trap in an Anti-Crystal Area, inside the Labyrinth of the 27th Floor, filled with continuously re-spawning monsters higher than their level. After Keita learned of the demise of his fellow guild mates, he committed suicide by jumping off the edge of an Aincrad floor. Months later, on Christmas Eve, Kirito learned of a revival item called the Divine Stone of Returning Soul that was dropped by the event boss Nicholas The Renegade and sought to search for it in hopes to revive his lover in the guild, Sachi, but was distraught that the item could only revive someone within their ten second end-phase, and not someone months ago. Fortunately, just hours later, a time-triggered recording crystal appeared in Kirito's shared inventory with Sachi just as he was about to leave on a suicide run against a Floor Boos. The message Sachi sent told him that she did not blame Kirito for her death, as she believed that her own character would have led to it eventually, thus persuading Kirito to live on.

Under the belief that he killed the members of the guild, Kirito refused to join other guilds for over a year until he was forced into Knights of the Blood after losing a duel against Heathcliff. After joining the guild and being asked by Asuna why he had avoided guilds so much even though he was a nice person, Kirito told Asuna about the demise of his former guild, also telling her that he believed that they would still be alive if he had never joined them, thus Asuna comforted him.

On October 9, 2024, Kirito was reminded of the deaths of the Black Cats of the Full Moon when The Army engaged the 74th Floor Boss, The Gleam Eyes, as The Army was unable to use their crystals and were slowly being killed off. The flashback occurred again on November 7, 2024, right before Kirito battled Heathcliff a second time after deducing his identity as Kayaba Akihiko.