It has been about six months since SAO launched, trapping its player base inside. Kirito has been playing solo for most of the time, but has now decided to join a guild, the Moonlit Black Cats, formed by a group who were friends in their school's computer club, and chose to band together in the game. Afraid of what their reaction may be, Kirito keeps his actual status as a beta tester, as well as his real level (much higher than that of the others) a secret, and agrees to help train Sachi, a timid spear user, to be a tank.
To continue to become stronger, Kirito would sneak out to higher-level dungeons at night to grind. During one such excursion, he receives a message from the guild leader, Keita: Sachi has gone missing!
Kirito finds her huddled up under a bridge in a village. Sachi expresses her fear of dying, to which Kirito assures her that she would not die and he would help her survive. To assuage her fears, he agrees to let her sleep by his side that night.
A few months later, the guild manages to save up enough money for a house in the Starting Town to use as their new base. While Keita, the guild's leader, departs for the Starting Town to make the purchase, the other members decide to explore a higher-level dungeon for loot. Kirito is reluctant to let them but decides to join them.
Unfortunately, disaster strikes when the group becomes trapped in a room filled with high-level monsters, a situation made all the worse by their teleport crystals being rendered unusable in the room. One by one, the Moonlit Black Cats are slaughtered, with Kirito watching as Sachi is the last to die. She says something to Kirito before dying, but Kirito cannot hear her...
When Kirito relays the fate of the guild to Keita, he also reveals the truth about himself. Keita, calling Kirito a Beater and blaming him for the death of his friends, throws himself off of Aincrad and dies in despair.
Several months later, on Christmas Eve, 2023, Kirito learns of an event boss, Nicholas the Renegade, that drops a particular item when defeated, one that can revive fallen players. Kirito becomes determined to defeat the boss and bring back Sachi, if for no other reason than to hear her last words, even if they were words of hatred.
While venturing towards the area where Nicholas would spawn, Kirito runs into a group of players clad in samurai armor. To his surprise, they are lead by Klein, who managed to reunite with his friends in the real world in-game and form a guild with them: WWFM (Fuurinkazan). Klein, relieved to see Kirito, offers to help him fight Nicholas, but Kirito steadfastly refuses. Their reunion is interrupted, however, by players from the Divine Dragon Alliance guild, notorious for going to almost any lengths to claim rare items. Klein offers to fend them off while Kirito fights Nicholas.
In the end, WWFM drives off the attackers, and Kirito emerges with the revival item. To Kirito's despair, however, the item is only effective for ten seconds after a player's HP reaches zero: it could not bring Sachi back like he had hoped. He gives the item to Klein and walks off dejectedly as Klein tearfully begs him to live on.
That midnight, an item suddenly appears in Kirito's inventory: a recorded message from Sachi! Sachi reveals that she had known for a long time that Kirito was a significantly higher level than her or the other guild members. As such, she knew he felt responsible for them, but reassures him that her demise was not his fault. She ends the message by thanking Kirito for spending time with her, and humming the theme to Rudolph the Red-Nosed Reindeer while Kirito breaks down.
Tropes in this episode include:
- All Deaths Final: Not even a revival item is enough to save Sachi.
- Badass Santa: Nicholas the Renegade is a Bonus Boss guarding a one-of-a-kind item that takes the form of Santa Claus. You'd better believe he's tough. The only gift he gives is pain.
- Bad Santa: This Santa Claus looks scary and he should because he's a bonus boss in a death game.
- Character Death: The Moonlit Black Cats are killed on their way to the Starting Town.
- Driven to Suicide: Keita after hearing of the death of his guild.
- Heroic BSoD: Kirito when Sachi and his friends from the Moonlit Black Cats are killed.
- Hope Spot: Kirito defeats Nicholas the Renegade and retrieves the item which can revive any player. Unfortunately for him, it only works if used on before ten seconds have passed from the point the player's HP reach zero, so Sachi can't be revived with it.
- I Let Gwen Stacy Die: After Sachi's death, Kirito is unable to cope with this loss until much later.
- Kill Em All: The Moonlit Black Cats are all dead by the end of the episode.
- Real Song Theme Tune: Sachi hums a version of "Rudolph, The Red-Nosed Reindeer" in her recorded message.