It seems like Tekken Series Producer Katsuhiro Harada spilled very big beans for Tekken Tag Tournament 2 in his official Twitter account, as he officially revealed the ability for players using Kazuya Mishima to transform into his alter ego, Devil (or a partial transformation at least), during a match in the game!
It seems that Kazuya has to be paired with Devil Jin in order for this trick to work, but anyone who's familiar with the Tekken series should know that it makes perfect sense, especially with dark background of the Devil Gene and tragic history of the Mishima Bloodline. It all started when Kazuya Mishima, having been abused and beaten by his father Heihachi, sought to gain the strength and power to defeat his dad by any means necessary. To this end, he literally made a deal with the Devil, and henceforth had evil power flowing in his veins... even passing on to his son, Jin Kazama, who becomes Devil Jin. The curse of the Devil Gene remained uncontrollable to the Mishima/ Kazama afflicted with it, but since Tekken 4, Kazuya was able to reconcile both halves AND gain access to that part of his power. Now we see that controlled aspect of his power in TTT2... but will it prove to be an advantage or a hindrance? Time will tell for sure when the game gets released in arcades this summer!