From Halopedia, the Halo wiki
The Hayabusa armor's advanced materials decreased its weight by nearly one-third, and was aesthetically designed after ancient Japanese samurai armor. It includes spiked shoulder pauldrons (correctly referred to as s'ode).
The Hayabusa armor's helmet was designed with a defensive and ultraviolet-protective visor. Like all UNSC helmets, the visor is the weakest part. Thus, a small visor was designed to be more difficult to accurately penetrate. As such, the small visor provides for better protection of the wearer as well as better camouflage. The Hayabusa was designed with greater emphasis on heavy lifting and extra-vehicular activity than the MJOLNIR. It is slightly slower and less dexterous than its MJOLNIR counterpart, though it is nonetheless highly effective and possesses most of the design features of the MJOLNIR Mark VI.
The Hayabusa is a powered battle armor system, similar to the MJOLNIR armor, except stemming from Project HAYABUSA as opposed to Project MJOLNIR. It was developed by the RKD group, an Earth-based think tank, in the year 2536, fifteen years before the MJOLNIR Mark V entered production. It was presented to the UNSC Ordnance Committee as an answer to the self-contained powered armor problem.
Originally, RKD developed Project HAYABUSA without knowledge of the classified Project MJOLNIR. After contacts were made between RKD and ONI's Materials Group, the two pooled their research resources, resulting in the creation of a MJOLNIR-compatible HAYABUSA variant. Featuring a number of stylistic and functional improvements, it became a crucial piece of hardware in the later years of the Human-Covenant War.
The Hayabusa armor permutation is a special unlock in Halo 3.
The Hayabusa armor was at some point intended for inclusion in Halo 4's multiplayer. Concept art was created for a [GEN2] iteration of the armor by artist Gabo Garza. A high-poly model of this armour was later created by an artist at Liquid Development, a studio which assisted in the creation of Halo 4's multiplayer armour sets. However, this version of Hayabusa has never been seen implemented within the game engine, and was not present in the final game.
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