nastrano

1. perversely; abnormally; oddly
   Komšija se u poslednje vreme ponaša nastrano. — The neighbor has been acting in a deviant way lately.
   To mi zvuči pomalo nastrano. — That sounds a bit perverse to me.

Usually disapproving; it can suggest oddness, eccentricity or perversion, including sexual perversion. For a neutral 'strangely' use čudno.