They were originally designed to explore the other side of the Boundary, as humans cannot survive there. However, they constantly met with failures, again and again, until finally one of the test subjects somehow managed to reach the heart of the Boundary, the Blue. By coming in contact with it, the Prime Field has developed emotions, grew a soul and obtained the power of the Eye, becoming godlike. Fearing its power, humans tried to destroy it to no avail and in the end have sealed it deep within the Boundary. This, however, was not the end. Humans realized that if they could tap into the power of the Blue, then they could dominate the battlefields with it. This is why the next Prime Field Contacts were outright weapons of mass destruction and not simple recon units. The moment that one would come out of the Kiln, its emotions would have been sealed, turning it into a puppet. The special weapon-type Prime Field Contacts were dubbed as Murakumo and Kusanagi, as they were meant to be weapons (swords) wielding a godlike power.
Shūichirō Ayatsuki attempted to create a separate system that would replace the Takamagahara System. Something that could enter the Boundary and even make contact with the Master Unit, the Kusanagi. Before Mitsuyoshi could stop the smelting process under Clavis' orders, the Black Beast had emerged.
The first Kusanagi was requested by Yūki Terumi and along with him, Relius Clover and Shūichirō Ayatsuki participated in its creation. It consisted of three notable elements, an Blue Grimoire, Zeroth Prime Field Model (第零型素体 Dai-Zero Gata Sotai), and Murakumo Unit. Its final refining process was scheduled for 2099/12/31. However, the Black Beast has emerged from an even deeper part of the Boundary, terminating the experiment. Its current status remains unknown.
Multiple Murakumo Units were made afterwards, typically by different companies; one such company being Seventh Agency with the creation of Mu -No. 12-. It is hinted that Relius Clover oversaw the development of Lambda -No. 11-. Relius, Kokonoe and Roy were present at the birth of Nu -No. 13-; as such, she can be seen as a collaborative effort between Seventh Agency and Relius.
Noel Vermillion was the first and only subject from the Murakumo-types to contain the true power of Blue. This allowed her to become the only known complete Kusanagi. Noel is referred to as the first Prime Field to contact the Master Unit.
As of now, only fourteen Murakumo Units have been created, and only three are known. Number 1 was destroyed by humanity using Sealed Armament: Izayoi and Nu's body was destroyed two times by Ragna the Bloodedge before the events of BlazBlue: Calamity Trigger.
- In BlazBlue: Calamity Trigger, "Dimensional Boundary Prime Field Contact" is localized as "Dimensional Boundary Contact Prime Field Force" and "Dimensional Boundary Contact Medium". Since Calamity Trigger Reconstruction in BlazBlue: Continuum Shift Extend, it's "Boundary Interface Prime Field Device". In BlazBlue: Centralfiction appears also "Dimensional Interface Prime Field Device" variant.