Currently there is no hold action for the dual blades, this should be how to switch to and from demon mode
現状/Current Status
Currently you have to press the special attack button to change to demon mode which means if you have a full special attack bar you cannot deactivate demon mode until you use your special, and some situations you would be beneficial to turn off demon mode and retain your special.
I think the best way to do it is to make it a hold and slide function, similar to other weapon activations. Not being able to cancel out of your Demon mode without consuming an full Special gauge makes it arbitrarily difficult.