Accel World, Vol. 2 (light novel): The Red Storm Princess: Accel World, cartea 2

Since meeting Kuroyukihime, Haruyuki has managed to grow up a bit. But suddenly this mature Haruyuki is confronted by Tomoko, an elementary school girl he's never met before--who calls him "big brother"?! When Kuroyukihime sees the two of them flirting, the look she gives Haruyuki is like a cold knife stabbing him in the gut! Meanwhile, in the Accelerated World, something very mysterious is taking place...