this could be minatos new jutsu
the new jutsu is IMO, a true s/t technique and not some kunai spread with minato and his KB warping all over the place using rasengans.
name of the jutsu: Rasen Senkou Chourinbu Kousanshiki.
translation: Spiral Flash Ring Dance Howl
Rasen = Spiral: pattern of the attack
Senkou = Flash: bright flash effect
Chourinbu = Ring: kunai spread forming a ring
Kousanshiki = Dance: takes 2 people to use / Howl: jutsus name needs to be said by both people or sound effect of the jutsu
this is how the jutsu is used.
minato and his KB form a ring with the ftg kunais around the target. after taking position they'd activate the jutsu with hand seals, creating a giant spiral eliminating anything inside the ftg kunai ring.
how effective would the jutsu be?
since the attack is a s/t jutsu, it would ignore any defense or durability they enemy has, making it possible to kill pretty much anything of any size. the negative part of this jutsu would be the preparation time, before it can be used.
what it looks like: the attack would be a large-scale kamui, similar to kakashis.