Zaelum
Want a way to use that new skill? Kill all of the friends you’ve made. Then revive them. Nobody said they had to stay dead. It just says you have to kill them. Stop their heart using something like lightning jutsu and then restart it. Just tell them you have a forbidden jutsu that requires the temporary sacrifice of someone close to you. You will only be stopping their heart for less than a minute then restarting it. With their temporary sacrifice, it will meet the conditions of activating the forbidden jutsu, granting power to use in the war. Allow them to see if it works. If it does, others will be willing to do it, too.