The Christmas Day Arc is the second story arc of Souyaku Toaru Majutsu no Index, covered in Souyaku Toaru Majutsu no Index Volume 2.[1]
Having fallen victim to a surprise attack from Anna Sprengel, Kamijou Touma has ended up in the hospital again, with an infection that threatens to kill him. At the same time, the spread of R&C Occultics is claiming victims throughout the city. With Touma's life at stake and science alone not enough to save him, Misaka Mikoto and Shokuhou Misaki team up to personally take on the Rosicrucian magician in the hopes of obtaining a cure, not knowing the odds stacked against them.