Necklace Sealing Technique
Debut
Manga	Chapter #438
Anime	Naruto Shippūden Episode #167
Appears in	Anime and Manga
Data
Classification	Fūinjutsu
Class	Supplementary
Users Yamato

Whenever Naruto Uzumaki entered into a tailed form, the First Hokage's Necklace activated this technique to restrain him. It is unknown if the technique just restrains Naruto until Yamato is able to suppress the Nine-Tails' influence or if it suppresses the influence by itself as the Nine-Tails cancelled the technique by crushing the necklace.^[1]

References

1. ↑ Naruto chapter 438, pages 2-4