How close are Turkish and Japanese? I know there is a proposed "Altaic language family"[1], but I'd love to hear the perspective of someone who actually knows two such languages.
Vowel harmony, no genders, no plurals, agglutinative etc are similar.
The only thing you need to learn is new words. The grammatical structure is same. Translation between Indo-European and Altaic is very hard. Translation beween Altaic languages is very easy.
[1] https://en.wikipedia.org/wiki/Altaic_languages