"The woman kisses you."
Translation:La virino kisas vin.
As someone coming from French (where object pronouns come before the verb) I'm glad that "La virino vin kisas" is acceptable
Because you are the object of the verb "kisi".
Whom does she kiss? You. You are the person being acted on during the kissing.
So vi (you, nominative) + -n (accusative marker) becomes "vin" (you, accusative).
if you study too long time, you will learn too much things... and confuse them too.
For the same reason that in English we sometimes use "he" and sometimes "him" -- case.
virino is the nominative case, used here because she is the subject of the sentence.
virinon is the accusative case and would be used, for example, if she is the direct object of a verb.
For example, Vi kisas la virinon would be "You kiss the woman" -- in that sentence, the woman is the object and so stands in the accusative case, while "you" are now the subject and so are in the nominative case (vi rather than vin).