The Flight Towards the Blue Sky Arc (蒼空への飛翔, Aozora e no Hisyō) is the fourth story arc of the Accel World series. The arc shows how Haruyuki and Takumu must deal with Seiji Noumi and find the truth of Chiyu's sudden betrayal. It also reveals the mystery about these certain Burst Linkers who don't show up on the matchmaking list. This arc spans the whole fourth novel of the Accel World series. The anime begins the arc in episode 20 and ends in episode 24.