Ruru

Ruru is a level 1 NPC of the 56th Floor. She accompagnies the heroes through much of the ordeal to clear the Geocrawler boss, and generally shows concern for most of the players.

Ruru's Lullaby
After Asuna is defeated in a duel with Kirito, Ruru sings a lullaby to Asuna:


 * "The southern travelling musician


 * With a lute in his hand


 * With a brush of silver threads


 * La, La-la, sleep awaits


 * Village chief with his long beard


 * Weapon shop uncle of greed


 * Kid's running through the plaza


 * A black cat up the roof


 * A robin singing atop a twig


 * Even the serpent, armored in iron


 * Da, da-da, da, da-da


 * Everyone's asleep."

It turns out that Ruru's lullaby is the secret to defeating the Geocrawler. By singing Ruru's Lullaby, the Geocrawler instantly falls asleep allowing the heroes to defeat it.