Sword Art Online Progressive Scherzo of Deep Night, Vol. 2 (manga)

The boss of the fifth floor of Sword Art Online will drop the Flag of Valor, a dangerously powerful item set to tip the delicate balance between the guilds! Hoping to preserve parity between the two mightiest guilds, Kirito organizes an impromptu raid to be the first to defeat the boss and seize the flag before it falls into the wrong hands...