User blog comment:Jopjopjop/Volume 18 Spoilers/@comment-3965848-20150511213228

So when Issei's arms turn that into a Dragon, the only to turn them back is to have someone (Akeno/Rias) suck the the enegy from the fingers right.

Since he can do the same with his feet, does that same person have to suck on his toes to turn them back.