This technique is a sealing jutsu that Danzo placed over his body, setting it to activate upon his death. The jutsu forms a large sphere around Danzo, drawing in everything within the spherical area and sealing it inside his corpse.

This jutsu has the opposite effect of Minato’s Four Symbols Seal, a technique which allows Naruto to draw out the Demon Fox’s chakra from within himself.

More info about this technique
Name: Ura Shisho Fuuinjutsu
Classification: Fuuinjutsu
Class: Offensive
Range: Short to Mid range
Users: Danzō Shimura