"A man kisses a woman."
Translation:Viro kisas virinon.
Duo is very straight-laced. Can't we get any "Viron kisas viron" au "virino kisas virinon"?
Viro is subject Viron is direct object
In the sententence the man does something to a woman, i.e. "Viro does something to virinon." It is not stating a woman is doing something to a man, i.e. "Virino does something to viron."