OK there's been a lot of threads about the sword slash (thunder god slash) that tobirama used to finish off izuna.many have been saying that's it's a s/t tech.i agree to this and would like to give people more reasons that it is true.
first of all the manga has made it clear that izuna and madara were equals when they had MS.so some one like izuna just wouldn't get hit by a simple sword slash and more die from it.right now i am too lazy to write about my ideas for a s/t technique that uses a sword but i am sure that people who watch various animes and read manga will have some idea.also on the topic i am not saying that minato did not create FTG.we have seen him studying/observing others jutsu's and recreating and improved version or a whole new technique.for example minato used the same concept of bijudama to create rassengan(an entirely new jutsu)that was very efficiently used with FTG.so what i am saying that minato might have learned s/t techniques by reading scrolls that tobirama left with info about his techniques but when minato learned them he modified it so it can be used with ease with his other techniques and with the changes he made to the s/t techniques he also changed the names.so the point's o wanted to conclude are:
-that tobirama can use s/t techniques
-tobirama used a s/t tech to finish of izuna.
-minato did create FTG.
-it's possible that minato learned S/T techs by reading scrolls that tobirama left.