- See also: Slither Inc.'s head office
Area D Highway is the area which was under siege by massive Maverick attacks. The player fights against Girouette in this area and acquires Biometal Model Z, allowing the player to Double Megamerge and become the Model ZX Mega Man. The soundtrack for this area is called Cinq Ville - c'est notre espoir -.
Most of the layout resembles the opening stage of the first Mega Man X game, a long highway with two battles against a flying mid-boss (King Flyer) resembling the Bee Blader. Area D-1 can be accessed from Area B-2 and Area C-2, and half of the area will be unavailable until the area's mission. Area D-2 has Slither Inc.'s head office, which can only be accessed in the final mission. Area D-3 gives access to Area G-1 and Area O-1, the path to Area G requiring a Yellow Card Key. There is a Transerver room between Area D-2 and D-3.
Area D-4 and D-5 are inside Slither Inc.'s head office and serve as the stage for the final mission, which culminates in the final battle between Vent/Aile and Serpent. All of the main mission bosses are fought at some point in this area before progressing to the final boss. Clearing this area's mission (which in effect, clears the game) unlocks Hard Mode; and if completed with both Vent and Aile, unlocks the ability to retain Model X in subsequent playthroughs. The soundtrack for this area is called Snake Eyes.
|King Flyer (mid-boss)|
|Fly Chopper (from King Flyer)|
- Life Up - In Area D-1.
Area O Highway 2 is a highway attacked by Slither Inc. after Serpent retrieved the Model W Core in Area M. Prometheus and Pandora are leading the Maverick attack, and they are fought together at the end of the area's mission, "Repel the Army". Deluxe Galleon Wing reappear there from Area X. Area O is accessed from Area D-3, and it has a Transerver room in Area O-2. The soundtrack for this area is called Black Burn.
|Prometheus and Pandora (boss)|
|Deluxe Galleon Wing (mid-boss)|
|Auto Counter ECO|
A Highway is attacked by Mavericks led by Thetis to obtain a Model W piece underwater. It bears some resemblance to the Highway from Mega Man ZX, and while it is located in the same city, it is unknown if is is the same one from Area D and Area O.
- ZXA Tunes booklet, Overloaded track notes
|Mega Man ZX|
|Vent / Aile (Humanoid) • Model X • Model ZX • Model HX • Model FX • Model LX • Model PX • Model OX|
|Hivolt the Raptoroid • Lurerre the Abysroid • Fistleo the Predatoroid • Purprill the Mandroid |
Hurricaune the Wolveroid • Leganchor the Gelroid • Flammole the Moleroid • Protectos the Goreroid
|Giga Aspis • Rayfly • Girouette (Model Z) • Prometheus • Pandora • Prometheus and Pandora • Serpent • Omega|
Deathtanz Mantisk • Hellbat Schilt • Childre Inarabitta • Blazin' Flizard
Pegasolta Eclair • Sol Titanion • Fenri Lunaedge • Noble Mandrago
|Database • Game Script (Vent's story • Aile's story) • Items • Manga • Overdrive Invoke System|