Okay, so we all know that Minato developed this jutsu (or could at least use it), and Hiruzen learned this jutsu. We also know that using this jutsu kills the user. So, my question is, how did they develope (if he did develope it)/learn this jutsu if it kills you? You can't practice it, and so this question has had me wondering for a while. How can you use a jutsu that you can only use once (as it kills you), as you have to use the jutsu to practice it so you know that it's going to work when you try to use it for real. How did Hiruzen know that the seal would work on Orochimaru if he couldn't use the jutsu before in his life (as seen with him and his shadow clones, even with them, he had to give up his soul). This has been driving me insane, so if anyone has information for me, or even idea's, I'd be happy to talk about this with you.