The Reaper Death Seal, initially created by the Uzumaki ... The caster of this jutsu was Minato Namikaze, the then Hokage and Naruto's father. He used this justu to trap Kurama.

But now, it seems like they finally have an answer, and it has to do with the Fourth Hokage, Minato Namikaze ... Naruto get a new form after Kurama's death? Naruto and Hinata in another dimension ...

The “Reaper”, aka Dead Demon Consuming Seal, is one of the darkest ... Much like the Reaper, Minato hasn’t appeared that often following his death caused by the Nine-Tailed Fox, though ...

Minato had to use the Reaper Death Seal to prevent Kurama from obliterating the Leaf Village, but the Nine-Tails decided to take out a crying Naruto to prevent this fate from befalling him.