manly vs manfully

manly is an adjective but manfully is not an adjective.

Word	Noun	Adjective	Verb	Adverb
manly	No	Yes	No	Yes
manfully	No	No	No	Yes

As adverbs, manly and manfully are synonyms defined as:

manly and manfully: in a manful manner; with qualities thought to befit a man

manly (adjective)	manfully (adjective)
possessing qualities befitting a man
characteristic of a man

manly (adverb)	manfully (adverb)
in a manful manner; with qualities thought to befit a man	in a manful manner; with qualities thought to befit a man