Its called "Yomotsu Heguri Arms" and its safe to say it will belong to Mitsuzane. It looks like a mish-mash of Grape- and Kiwi-Arms and apparently it can summon the weapons of the Overlords, alongside the Budou Ryuhou and the Kiwi Gekirin. Its like a dark version of Kiwami, and its also said that the armor feeds upon the life of its user.
All of this is, except for the fact that this Arms exists is still unconfirmed, so take it with a grain of salt.
But this arms will most likely appear in the first episode of September, episode 44.
Why Micchy dons this arms, and how, is still unclear. Maybe he uses it to battle the overlords, or he takes their place. I could see him killing Redyue, that would be awesome.
And if Micchy uses this arms with a regular Sengoku Driver, what will happen to Melon Energy and the Genesis Driver? Will it be destroyed when Micchy defeats the ghost of his brother, or will Takatora return to claim his armor back?
I'm very interested to see how this turns out.