manana vs hereafter

manana and hereafter both are nouns.

Word	Noun	Adjective	Verb	Adverb
manana	Yes	No	No	No
hereafter	Yes	No	No	Yes

As nouns, hereafter is a hypernym of manana; that is, hereafter is a word with a broader meaning than manana:

Other hypernyms of manana include future, futurity, time to come.

manana (noun)	hereafter (noun)
an unspecified time in the future	the time yet to come
	life after death

manana (adverb)	hereafter (adverb)
	in a subsequent part of this document or statement or matter etc.
	following this in time or order or place; after this
	in a future life or state