Board Thread:Rebirth: Applications/@comment-24019243-20141016022001/@comment-24019243-20141027205358

Ok, Shinzen was able to learn it. However, during the war Konohagakure had a spy inside of iwa's military, he didn't know that Shinzen had already began learning the technique, but he informed Konoha that iwa was finding a way to teach their ninja the FTG technique. So then in a tactical matter, Konoha sent in their spy to plant many Explosive Seals around the lab and then destroy it. He succeeded and so no one else could learn it. After weeks though he was found and eliminated.