Board Thread:BlazBlue: Centralfiction/@comment-8695373-20161004174202

So, I've found something on Japanese threads, I have no idea if this info is right, or if it's speculation.
 * Susanoo's Overdrive temporarily releases all of his locks (on those icons)
 * His Unlimited form is unlocked by default
 * His heat gauge has the form of the sword. Susanoo consumes his heat gauge to use the sword (like the sword from Terumi's Astral)
 * The more heat he has, the more locks are released.

Update: (info not confirmed) By gaining heat, Susanoo releases locks from the buttons that can be used for his Drive. So, he has the "right" arrow unlocked with 0 heat, that means he can use 6D with 0 heat. 