These two words, which sound so alike, are actually nearly opposites. Ingenuous means “to be artless, simple, innocent; lacking in cunning, guile, or worldliness.” It also means “openly straightforward or frank; candid.”
If you are ingenuous, you have an inability to mask your feelings; you are not devious
Ingenious means “to be particularly imaginative, clever, inventive.”
Example: Her idea was so ingenious that it went completely over the head of her ingenuous new assistant.