Unicode encodes g with tilde with a combining diacritical mark (U+0303◌̃COMBINING TILDE), rather than a precomposed character. As such, the tilde may not align properly with some typefaces and systems. Additionally, owing to the difficulties in inputting this character, Guarani speakers often omit the diacritic altogether.[1]
^Redish, Laura; Lewis, Orrin. "Guarani Pronunciation and Spelling Guide". Native Languages of the Americas. Retrieved 16 September 2015. Most Guarani speakers don't use this character, instead spelling this sound the same as a plain g.