"Rockman.EXE Beast+" is the fifth and final season of the "Rockman.EXE" anime series, serving as a direct continuation of "Rockman.EXE Beast." The story revolves around Lan Hikari and his NetNavi, MegaMan.EXE, as they face new challenges in the aftermath of the events from the previous season. The narrative begins with the introduction of a mysterious entity known as Nebula Grey, a powerful and destructive force that threatens both the cyber and real worlds. Nebula Grey is revealed to be a fusion of the remnants of the Darkloids and the Cybeasts, creating an unprecedented threat.

Lan and MegaMan, alongside their friends, must confront this new menace while dealing with the resurgence of the Cybeasts, Falzar and Gregar. These ancient entities, previously thought to be neutralized, re-emerge and begin to wreak havoc once again. The series explores the concept of "Beast Out," a state where MegaMan temporarily transforms into a more powerful form by harnessing the energy of the Cybeasts. However, this transformation comes with significant risks, as it threatens to consume MegaMan's consciousness and turn him into a mindless beast.

The plot intensifies as Nebula Grey begins to manipulate individuals and organizations, including the criminal group WWW, to further its agenda of global domination. Lan and MegaMan must navigate a series of battles and alliances, including working with former enemies, to prevent Nebula Grey from achieving its goals. The story also delves into the emotional and psychological struggles of the characters, particularly Lan, who must grapple with the potential loss of MegaMan to the Beast Out state.

Key characters include Lan Hikari, the determined and resourceful protagonist; MegaMan.EXE, his loyal and courageous NetNavi; Chaud Blaze and ProtoMan.EXE, Lan's rival and his powerful NetNavi; and Mayl Sakurai and Roll.EXE, Lan's close friend and her supportive NetNavi. The series also features returning antagonists such as Dr. Regal, who plays a pivotal role in the resurgence of the Cybeasts and the emergence of Nebula Grey.

The narrative builds toward a climactic showdown between MegaMan and Nebula Grey, with the fate of both the cyber and real worlds hanging in the balance. The resolution of the series ties together the overarching themes of friendship, sacrifice, and the coexistence of technology and humanity, bringing the "Rockman.EXE" saga to a conclusive and impactful end.